Contributing docs (#254)

* WIP

* Final version

Author: RunDevelopment

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Create a report to help us improve.
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Information:**
+- ESLint version:
+- `eslint-plugin-regexp` version:
+
+**Description**
+<!--
+
+A clear and concise description of what the bug is and how to reproduce it.
+If applicable, add examples/screenshots to help explain your problem.
+
+-->

.github/ISSUE_TEMPLATE/feature_request.md

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+---
+name: Feature request
+about: Suggest a new feature.
+title: ''
+labels: enhancement
+assignees: ''
+
+---
+
+**Description**
+<!--
+A clear and concise description of the new feature.
+Also give a few code examples.
+-->

.github/ISSUE_TEMPLATE/new_rule_request.md

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+---
+name: New rule request
+about: Suggest a new rule.
+title: ''
+labels: enhancement, new rule
+assignees: ''
+
+---
+
+**Motivation**
+<!-- A clear and concise description of the problem the new rule is supposed to solve. -->
+
+**Description**
+<!-- A clear and concise description of the new rule. -->
+
+**Examples**
+
+<!-- Add a few examples of regexes that the rule does and does not report. -->
+
+```js
+/* ✓ GOOD */
+var foo = /regex/
+
+/* ✗ BAD */
+var foo = /regex/
+```

.github/ISSUE_TEMPLATE/other.md

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+---
+name: Other
+about: An issue that doesn't fit into the other categories.
+title: ''
+labels: ''
+assignees: ''
+
+---

CONTRIBUTING.md

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+# Contributing
+
+👍🎉 First off, thanks for taking the time to contribute! 🎉👍
+
+
+## Reporting bugs
+
+To report a bug, [open an issue][new-issue].
+
+If you are unsure whether something is a bug or not, please [open an issue][new-issue]. Insufficient documentation is also a bug.
+
+
+## Suggesting new features
+
+New features can be a new rule, anew option for an existing rule, or new functionality for existing rules.
+
+To suggest a new feature, [open an issue][new-issue].
+
+
+## Making pull requests
+
+(If this is your first pull request on GitHub, checkout [this guide](https://github.com/firstcontributions/first-contributions).)
+
+
+### Getting started
+
+- This is a TypeScript project. You need to have a recentish version of [Node.js](https://nodejs.org/) and npm installed.
+- Install all project and development dependencies by running `npm ci`.
+- Test that everything is installed correctly by running `npm test`.
+
+We use [ESLint](https://eslint.org/) and [Prettier](https://prettier.io/) to lint and format our code base. They will be automatically installed as dependencies but you might need additional editor plugins for a good IDE experience. We recommend using [VSCode](https://code.visualstudio.com/) together with the [ESLint plugin](https://marketplace.visualstudio.com/items?itemName=dbaeumer.vscode-eslint) for a great editing experience.
+
+
+### Creating a new rule
+
+The following steps will walk you through the process of creating a new rule.
+
+1.  Run `npm run new <rule-name>`:
+
+    This will automatically create 3 files:
+
+    1. `lib/rules/rule-name.ts` - Implementation + meta information (name, category, short desc, etc.)
+    1. `tests/lib/rules/rule-name.ts` - Functional tests
+    1. `docs/rules/rule-name.md` - Documentation
+
+    These 3 files contain all the information about your new rule. You only need to touch these 3 files to add your rule.
+
+1.  Add meta information:
+
+    Fill in the rule's meta information in the `meta` object. This includes a short description, its category, type, and more.
+
+    Note: Do not set `recommended: true`. This will add your rule to the `regex/recommended` configuration. We view additions to the `regex/recommended` configuration as breaking changes. If you want your rule to be included in the `regex/recommended` configuration in the next major release, leave the generated TODO comment as is.
+
+    Once you added a short description and the category, run `npm run update`. This will update a few generated files to include your rule in the website and more.
+
+1.  Implement your rule:
+
+    The `createVisitor` function will be where you implement your rule. The `regexpContext` object contains information and methods that you will need for static analysis, reporting, and fixing. Use `messageId`s for report and suggestion messages.
+
+    The [`no-empty-capturing-group`](./lib/rules/no-empty-capturing-group.ts) and [`no-octal`](./lib/rules/no-octal.ts) rules are good examples to see how we usually implement rules.
+
+1.  Test your rule:
+
+    Add test for every feature and option of your rule. (We use [ESLint's `RuleTester`](https://eslint.org/docs/developer-guide/nodejs-api#ruletester) for testing rules.)
+
+    Use `npm test` to run all tests.
+
+1.  Document your rule:
+
+    The documentation should contain a description of the rule and the problem it detects/solves, examples, all features, all options, and any additional information relevant to the rule.
+
+    You can view the documentation live in your browser by running `npm run build && npm run docs:watch`. The live view will automatically update when you make changes to the documentation. However, you have to re-run the command to see changes to the rule implementation.
+
+
+### Updating documentation
+
+Almost all Markdown files of our website and the project `README.md` are partially or completely generated.
+
+The following files are completely generated and must not be modified directly:
+
+- `docs/README.md` - change this section of the project `README.md` instead.
+- `docs/rules/README.md`
+- `docs/user-guide/README.md` - change this section of the project `README.md` instead.
+
+The following files are partially generated:
+
+- `README.md`: The rules table is generated.
+- `docs/rules/*.md`: Everything above the ":book: Rule Details" heading and below the ":mag: Implementation" heading is generated.
+
+Only change the non-generated parts in these files.
+
+After you changed the documentation, run `npm run update` to update all generated files. Be sure to always run this command before you commit any documentation changes.
+
+You can view changes to the website locally by running `npm run docs:watch`.
+
+
+### Testing
+
+Aside from `npm test`, there are also a few other ways to manually test new features, changes, and new rules.
+
+1.  `npm run build && npm run docs:watch`:
+
+    The documentation page of each rule includes interactive examples. You can also use your local version of [the playground](https://ota-meshi.github.io/eslint-plugin-regexp/playground/) to for testing.
+
+1.  Test your rule and the whole plugin by installing it.
+
+    If there is a project/code base you want to test your rule/the entire plugin on, then installing this project will be the right solution.
+
+    [Setup ESLint](https://eslint.org/docs/user-guide/getting-started) in the target project. Instead of installing the `eslint-plugin-regexp` from the npm registry, install your local `eslint-plugin-regexp` project using the relative path to the project.
+
+    Example:
+
+    ```
+    projects/
+    ├── target/
+    |   └── package.json
+    └── eslint-plugin-regexp/
+        └── package.json
+    ```
+
+    ```console
+    projects/target$ npm i -D ../eslint-plugin-regexp
+    ```
+
+    Note: If you make changes to the implementation of a rule, you'll have to run `npm run build` before these changes show up in the target project.
+
+
+<!-- Important links -->
+
+[new-issue]: https://github.com/PrismJS/prism/issues/new/choose