Add spell checking for articles

This commit adds spell checking to all the other prose and
markdown checks currently in place.
As spell checking is a pretty pedantic issue, often marking
jargon (like 501c3, BDFL, or grantmaking) and project and
product names (like Homebrew, Kubernetes, or WordPress),
a personal `dictionary.txt` is included in `test/` with
exceptions for the articles.

URLs, filepaths, @mentions, emoji, and text in block quotes
(as those are used for quotes in the articles) are excluded
from the spell checking.

The spell checking highlighted some cases that I changed:

*   All alt text of images is now properly cases if they
    start the paragraph
*   Typo `sizeable` > `sizable` (former is GB English, latter is
    US English)
*   Casing of `reddit` > `Reddit` (latter seems to be used more)
*   Casing of `pypa` > `PyPA` (latter seems to be used more)
*   Casing of `eslint` > `ESLint` (latter is the official casing)
*   Casing of `READMES` > `READMEs` (plural `s` is now cased just
    like `PRs` and `APIs`)
*   Casing of `ok` > `OK` (latter is the propper spelling)
*   Spelling of `PostgreSQL` > `Postgres` (both were used throughout,
    the latter seems simpler and is just as well known)
*   Hyphen in `tradeoffs` > `trade-offs` (both could probably be used,
    but the latter is more often used)
*   Latin `de minimis` > `minimal` (this section is about law, so the
    Latin makes sense, but it’s also a phrase I had to look up, so
    I’m guessing other people would have to as well)
*   Space in `pageviews` > `page views` (former is more about the
    metrics in Google Analytics I believe, latter is just as good?)
*   Space in `datasets` > `data sets` (both work, but latter is more
    common?)

Author: wooorm

_articles/best-practices.md

@@ -119,7 +119,7 @@ If you don't want to accept a contribution:
 
 You shouldn't need more than 1-2 sentences to respond. For example, when a user of [celery](https://github.com/celery/celery/) reported a Windows-related error, @berkerpeksag [responded with](https://github.com/celery/celery/issues/3383):
 
-![celery screenshot](/assets/images/best-practices/celery.png)
+![Celery screenshot](/assets/images/best-practices/celery.png)
 
 If the thought of saying no terrifies you, you're not alone. As @jessfraz [put it](https://blog.jessfraz.com/post/the-art-of-closing/):
 

_articles/building-community.md

@@ -20,7 +20,7 @@ A welcoming community is an investment into your project's future and reputation
 
 One way to think about your project's community is through what @MikeMcQuaid calls the [contributor funnel](https://speakerdeck.com/mikemcquaid/the-open-source-contributor-funnel):
 
-![contributor funnel](/assets/images/building-community/contributor_funnel_mikemcquaid.png)
+![Contributor funnel](/assets/images/building-community/contributor_funnel_mikemcquaid.png)
 
 As you build your community, consider how someone at the top of the funnel (a potential user) might theoretically make their way to the bottom (an active maintainer). Your goal is to reduce friction at each stage of the contributor experience. When people have easy wins, they will feel incentivized to do more.
 
@@ -80,7 +80,7 @@ Try to be responsive when someone files an issue, submits a pull request, or ask
 
 Even if you can't review the request immediately, acknowledging it early helps increase engagement. Here's how @tdreyno responded to a pull request on [Middleman](https://github.com/middleman/middleman/pull/1466):
 
-![middleman pull request](/assets/images/building-community/middleman_pr.png)
+![Middleman pull request](/assets/images/building-community/middleman_pr.png)
 
 [A Mozilla study found that](https://docs.google.com/presentation/d/1hsJLv1ieSqtXBzd5YZusY-mB8e1VJzaeOmh8Q4VeMio/edit#slide=id.g43d857af8_0177) contributors who received code reviews within 48 hours had a much higher rate of return and repeat contribution.
 
@@ -130,7 +130,7 @@ Good documentation only becomes more important as your community grows. Casual c
 
 In your CONTRIBUTING file, explicitly tell new contributors how to get started. You may even want to make a dedicated section for this purpose. [Django](https://github.com/django/django), for example, has a special landing page to welcome new contributors.
 
-![django new contributors page](/assets/images/building-community/django_new_contributors.png)
+![Django new contributors page](/assets/images/building-community/django_new_contributors.png)
 
 In your issue queue, label bugs that are suitable for different types of contributors: for example, [_"first timers only"_](https://medium.com/@kentcdodds/first-timers-only-78281ea47455#.g1k01jy05), _"good first bug"_, or _"documentation"_. [These labels](https://github.com/librariesio/libraries.io/blob/6afea1a3354aef4672d9b3a9fc4cc308d60020c8/app/models/github_issue.rb#L8-L14) make it easy for someone new to your project to quickly scan your issues and get started.
 
@@ -158,11 +158,11 @@ See if you can find ways to share ownership with your community as much as possi
 
 * **Resist fixing easy (non-critical) bugs.** Instead, use them as opportunities to recruit new contributors, or mentor someone who'd like to contribute. It may seem unnatural at first, but your investment will pay off over time. For example, @michaeljoseph asked a contributor to submit a pull request on a [Cookiecutter](https://github.com/audreyr/cookiecutter) issue below, rather than fix it himself.
 
-![cookiecutter issue](/assets/images/building-community/cookiecutter_submit_pr.png)
+![Cookiecutter issue](/assets/images/building-community/cookiecutter_submit_pr.png)
 
 * **Start a CONTRIBUTORS or AUTHORS file in your project** that lists everyone who's contributed to your project, like [Sinatra](https://github.com/sinatra/sinatra/blob/master/AUTHORS.md) does.
 
-* If you've got a sizeable community, **send out a newsletter or write a blog post** thanking contributors. Rust's [This Week in Rust](https://this-week-in-rust.org/) and Hoodie's [Shoutouts](http://hood.ie/blog/shoutouts-week-24.html) are two good examples.
+* If you've got a sizable community, **send out a newsletter or write a blog post** thanking contributors. Rust's [This Week in Rust](https://this-week-in-rust.org/) and Hoodie's [Shoutouts](http://hood.ie/blog/shoutouts-week-24.html) are two good examples.
 
 * **Give every contributor commit access.** @felixge found that this made people [more excited to polish their patches](http://felixge.de/2013/03/11/the-pull-request-hack.html), and he even found new maintainers for projects that he hadn't worked on in awhile.
 

_articles/finding-users.md

@@ -27,7 +27,7 @@ Remember that people get involved as users, and eventually contributors, because
 
 For example, @robb uses code examples to clearly communicate why his project, [Cartography](https://github.com/robb/Cartography), is useful:
 
-![cartography readme](/assets/images/finding-users/cartography.jpg)
+![Cartography README](/assets/images/finding-users/cartography.jpg)
 
 For a deeper dive into messaging, check out Mozilla's ["Personas and Pathways"](http://mozillascience.github.io/working-open-workshop/personas_pathways/) exercise for developing user personas.
 
@@ -60,15 +60,15 @@ If you don't wish to set up these channels for your project yet, promote your ow
 
 If your project is hosted on GitHub, you can use [GitHub Pages](https://pages.github.com/) to easily make a website. [Yeoman](http://yeoman.io/), [Vagrant](https://www.vagrantup.com/), and [Middleman](https://middlemanapp.com/) are [a few examples](https://github.com/showcases/github-pages-examples) of excellent, comprehensive websites.
 
-![vagrant homepage](/assets/images/finding-users/vagrant_homepage.png)
+![Vagrant homepage](/assets/images/finding-users/vagrant_homepage.png)
 
 Now that you have a message for your project, and an easy way for people to find your project, let's get out there and talk to your audience!
 
 ## Go where your project's audience is (online)
 
 Online outreach is a great way to share and spread the word quickly. Using online channels, you have the potential to reach a very wide audience.
 
-Take advantage of existing online communities and platforms to reach your audience. If your open source project is a software project, you can probably find your audience on [Stack Overflow](http://stackoverflow.com/), [reddit](http://www.reddit.com), [Hacker News](https://news.ycombinator.com/), or [Quora](https://www.quora.com/). Find the channels where you think people will most benefit from or be excited about your work.
+Take advantage of existing online communities and platforms to reach your audience. If your open source project is a software project, you can probably find your audience on [Stack Overflow](http://stackoverflow.com/), [Reddit](http://www.reddit.com), [Hacker News](https://news.ycombinator.com/), or [Quora](https://www.quora.com/). Find the channels where you think people will most benefit from or be excited about your work.
 
 <aside markdown="1" class="pquote">
   <img src="https://avatars1.githubusercontent.com/u/169328?v=3&s=400" class="pquote-avatar" alt="avatar">
@@ -90,7 +90,7 @@ If nobody pays attention or responds to your initial outreach, don't get discour
 
 ## Go where your project's audience is (offline)
 
-![public speaking](/assets/images/finding-users/public_speaking.jpg)
+![Public speaking](/assets/images/finding-users/public_speaking.jpg)
 
 Offline events are a popular way to promote new projects. It's a great way to reach an engaged audience and build deeper human connections, especially if you are interested in reaching developers.
 

_articles/how-to-contribute.md

@@ -97,7 +97,7 @@ Even if you like to write code, other types of contributions are a great way to
 * Write and improve the project's documentation
 * Curate a folder of examples showing how the project is used
 * Start a newsletter for the project, or curate highlights from the mailing list
-* Write tutorials for the project, [like pypa's contributors did](https://github.com/pypa/python-packaging-user-guide/issues/194)
+* Write tutorials for the project, [like PyPA's contributors did](https://github.com/pypa/python-packaging-user-guide/issues/194)
 * Write a translation for the project's documentation
 
 <aside markdown="1" class="pquote">
@@ -111,7 +111,7 @@ Even if you like to write code, other types of contributions are a great way to
 ### Do you like organizing?
 
 * Link to duplicate issues, and suggest new issue labels, to keep things organized
-* Go through open issues and suggest closing old ones, [like @nzakas did for eslint](https://github.com/eslint/eslint/issues/6765)
+* Go through open issues and suggest closing old ones, [like @nzakas did for ESLint](https://github.com/eslint/eslint/issues/6765)
 * Ask clarifying questions on recently opened issues to move the discussion forward
 
 ### Do you like to code?
@@ -123,7 +123,7 @@ Even if you like to write code, other types of contributions are a great way to
 
 ### Do you like helping people?
 
-* Answer questions about the project on e.g., Stack Overflow ([like this Postgres example](http://stackoverflow.com/questions/18664074/getting-error-peer-authentication-failed-for-user-postgres-when-trying-to-ge)) or reddit
+* Answer questions about the project on e.g., Stack Overflow ([like this Postgres example](http://stackoverflow.com/questions/18664074/getting-error-peer-authentication-failed-for-user-postgres-when-trying-to-ge)) or Reddit
 * Answer questions for people on open issues
 * Help moderate the discussion boards or conversation channels
 
@@ -181,7 +181,7 @@ A project also has documentation. These files are usually listed in the top leve
 
 * **LICENSE:** By definition, every open source project must have an [open source license](https://choosealicense.com). If the project does not have a license, it is not open source.
 * **README:** The README is the instruction manual that welcomes new community members to the project. It explains why the project is useful and how to get started.
-* **CONTRIBUTING:** Whereas READMES help people _use_ the project, contributing docs help people _contribute_ to the project. It explains what types of contributions are needed and how the process works. While not every project has a CONTRIBUTING file, its presence signals that this is a welcoming project to contribute to.
+* **CONTRIBUTING:** Whereas READMEs help people _use_ the project, contributing docs help people _contribute_ to the project. It explains what types of contributions are needed and how the process works. While not every project has a CONTRIBUTING file, its presence signals that this is a welcoming project to contribute to.
 * **CODE_OF_CONDUCT:** The code of conduct sets ground rules for participants' behavior associated and helps to facilitate a friendly, welcoming environment. While not every project has a CODE_OF_CONDUCT file, its presence signals that this is a welcoming project to contribute to.
 * **Other documentation:** There might be additional documentation, such as tutorials, walkthroughs, or governance policies, especially on bigger projects.
 
@@ -399,7 +399,7 @@ Before you open an issue or pull request, or ask a question in chat, keep these
 >
 > 😢 _"X is broken! Please fix it."_
 
-**Do your homework beforehand.** It's ok not to know things, but show that you tried. Before asking for help, be sure to check a project's README, documentation, issues (open or closed), mailing list, and search the internet for an answer. People will appreciate when you demonstrate that you're trying to learn.
+**Do your homework beforehand.** It's OK not to know things, but show that you tried. Before asking for help, be sure to check a project's README, documentation, issues (open or closed), mailing list, and search the internet for an answer. People will appreciate when you demonstrate that you're trying to learn.
 
 > 😇 _"I'm not sure how to implement X. I checked the help docs and didn't find any mentions."_
 >

_articles/leadership-and-governance.md

@@ -60,7 +60,7 @@ Formalizing your leadership roles helps people feel ownership and tells other co
 
 For a smaller project, designating leaders can be as simple as adding their names to your README or a CONTRIBUTORS text file.
 
-For a bigger project, if you have a website, create a team page or list your project leaders there. For example, [PostgreSQL](https://github.com/postgres/postgres/) has a [comprehensive team page](https://www.postgresql.org/community/contributors/) with short profiles for each contributor.
+For a bigger project, if you have a website, create a team page or list your project leaders there. For example, [Postgres](https://github.com/postgres/postgres/) has a [comprehensive team page](https://www.postgresql.org/community/contributors/) with short profiles for each contributor.
 
 If your project has a very active contributor community, you might form a "core team" of maintainers, or even subcommittees of people who take ownership of different issue areas (ex. security, issue triaging, or community conduct). Let people self-organize and volunteer for the roles they're most excited about, rather than assigning them.
 
@@ -105,7 +105,7 @@ There are three common governance structures associated with open source project
 
 * **Liberal contribution:** Under a liberal contribution model, the people who do the most work are recognized as most influential, but this is based on current work and not historic contributions. Major project decisions are made based on a consensus seeking process (discuss major grievances) rather than pure vote, and strive to include as many community perspectives as possible. Popular examples of projects that use a liberal contribution model include [Node.js](https://nodejs.org/en/foundation/) and [Rust](https://www.rust-lang.org/en-US/).
 
-Which one should you use? It's up to you! Every model has advantages and tradeoffs. And although they may seem quite different at first, all three models have more in common than they seem. If you're interested in adopting one of these models, check out these templates:
+Which one should you use? It's up to you! Every model has advantages and trade-offs. And although they may seem quite different at first, all three models have more in common than they seem. If you're interested in adopting one of these models, check out these templates:
 
 * [BDFL model template](http://oss-watch.ac.uk/resources/benevolentdictatorgovernancemodel)
 * [Meritocracy model template](http://oss-watch.ac.uk/resources/meritocraticgovernancemodel)

_articles/legal.md

@@ -34,7 +34,7 @@ Finally, your project may have dependencies with license requirements that you w
 
 When you [create a new project](https://help.github.com/articles/creating-a-new-repository/) on GitHub, you have the option to make the repository **private** or **public**.
 
-![create repository](/assets/images/legal/repo-create-name.png)
+![Create repository](/assets/images/legal/repo-create-name.png)
 
 **Making your GitHub project public is not the same as licensing your project.** Public projects are covered by [GitHub's Terms of Service](https://help.github.com/articles/github-terms-of-service/#f-copyright-and-content-ownership), which allows others to view and fork your project, but your work otherwise comes with no permissions.
 
@@ -86,7 +86,7 @@ For example, as your project grows it adds dependencies or users, or your compan
 
 **Your project's existing license.** If your project's existing license is compatible with the license you want to change to, you could just start using the new license. That's because if license A is compatible with license B, you'll comply with the terms of A while complying with the terms of B (but not necessarily vice versa). So if you're currently using a permissive license (e.g., MIT), you could change to a license with more conditions, so long as you retain a copy of the MIT license and any associated copyright notices (i.e., continue to comply with the MIT license's minimal conditions). But if your current license is not permissive (e.g., copyleft, or you don't have a license) and you aren't the sole copyright holder, you couldn't just change your project's license to MIT. Essentially, with a permissive license the project's copyright holders have given permission in advance to change licenses.
 
-**Your project's existing copyright holders.** If you're the sole contributor to your project then either you or your company is the project's sole copyright holder. You can add or change to whatever license you or your company wants to. Otherwise there may be other copyright holders that you need agreement from in order to change licenses. Who are they? People who have commits in your project is a good place to start. But in some cases copyright will be held by those people's employers. In some cases people will have only made _de minimis_ contributions, but there's no hard and fast rule that contributions under some number of lines of code are not subject to copyright. What to do? It depends. For a relatively small and young project, it may be feasible to get all existing contributors to agree to a license change in an issue or pull request. For large and long-lived projects, you may have to seek out many contributors and even their heirs. Mozilla took years (2001-2006) to relicense Firefox, Thunderbird, and related software.
+**Your project's existing copyright holders.** If you're the sole contributor to your project then either you or your company is the project's sole copyright holder. You can add or change to whatever license you or your company wants to. Otherwise there may be other copyright holders that you need agreement from in order to change licenses. Who are they? People who have commits in your project is a good place to start. But in some cases copyright will be held by those people's employers. In some cases people will have only made minimal contributions, but there's no hard and fast rule that contributions under some number of lines of code are not subject to copyright. What to do? It depends. For a relatively small and young project, it may be feasible to get all existing contributors to agree to a license change in an issue or pull request. For large and long-lived projects, you may have to seek out many contributors and even their heirs. Mozilla took years (2001-2006) to relicense Firefox, Thunderbird, and related software.
 
 Alternatively, you can have contributors agree in advance (via an additional contributor agreement -- see below) to certain license changes under certain conditions, beyond those allowed by your existing open source license. This shifts the complexity of changing licenses a bit. You'll need more help from your lawyers up front, and you'll still want to clearly communicate with your project's stakeholders when executing a license change.