Add CONTIBUTING.md

Author: SpeedJack

CONTRIBUTING.md

@@ -0,0 +1,42 @@
+# Contributing to GridShow
+
+## First setup
+
+1. You need [XenForo 2.x](https://xenforo.com/). You can setup a Scotch Box
+   environment as described in the [Xenforo 2.x Development
+   Documentation](https://xenforo.com/xf2-docs/dev/scotchbox/)
+2. Fork GridShow
+3. Move in the `src/addon/` folder of your development enviroment and `mkdir Inforge && cd Inforge`
+4. `git clone https://github.com/<your-username>/GridShow && cd GridShow`
+5. `git remote add upstream https://github.com/InforgeNet/GridShow`
+
+## Pull request
+
+Each time you want to submit a pull request, do the following:
+
+1. Download latest upstream modifications: `git fetch upstream`
+2. Ceate a new branch: `git checkout -b whatever-you-want-feature upstream/master`
+3. Make you changes, add them and commit
+4. `git push -u origin whatever-you-want-feature`
+5. Visit `https://github.com/<your-username>/GridShow` and create a new pull request
+
+### Commit message
+
+Follow these guidelines to write a proper commit message: [How to Write a Git
+Commit Message](https://chris.beams.io/posts/git-commit/).
+
+### Code style
+
+General guidelines:
+
+* Indent code with a **single tab**
+* Avoid brackets when they are not necessary
+* Try to keep lines under 80 columns, assuming a tab width equal to 8 spaces
+  (yes!)
+* Follow the [XenForo 2.x](https://xenforo.com/xf2-docs/dev/) code style
+  conventions
+* In general, I like the [Linux Kernel Coding
+  Style](https://www.kernel.org/doc/html/latest/process/coding-style.html) and
+  try to adapt it to PHP, JS and every other C-like language
+* Check out the code already in the repository and try to follow the same style
+* Use common sense

README.md

@@ -7,17 +7,18 @@ XenForo 2.x AddOn to show a grid of tiles in homepage.
 
 Download the [latest
 release](https://github.com/InforgeNet/GridShow/releases/latest) and follow the
-instructions of [installing an add-on for
-XenForo2](https://xenforo.com/xf2-docs/manual/add-ons/)
+instructions for [installing an add-on for
+XenForo2](https://xenforo.com/xf2-docs/manual/add-ons/).
 
 For development, fork the repository and then clone the fork in the
-`src/addon/Inforge/GridShow` directory of your development board.
+`src/addon/Inforge/GridShow` directory of your development board. For more
+informations, see the [Contributing Guidelines](CONTRIBUTING.md).
 
 ## Usage
 
 In the admin panel you will find the _GridShow_ menu. Here, you can add new
 tiles to display to your users. You can set as many tiles as you want but the
-add-on will display only the first 12.
+add-on will display only the first 12 tiles.
 
 Users must have the `View tiles` permission set to view the tiles in homepage
 (default enabled). Admins must have the `Manage GridShow tiles` permission set