[Docs] Add CONTRIBUTING.md

CONTRIBUTING.md

@@ -0,0 +1,108 @@
+# Contributing
+
+Thank you for considering contributing to Symfony UX! 
+
+Symfony UX is an open source, community-driven project, and we are happy to receive contributions from the community!
+
+> [!TIP]
+> It's a good idea to read the [Symfony's Contribution Guide](https://symfony.com/doc/current/contributing/index.html) first, even if not all of it applies to Symfony UX and should be adapted to this project (e.g.: Symfony UX has only one base branch, `2.x`).
+
+## Reporting an issue
+
+If you either find a bug, have a feature request, or need help/have a question, please [open an issue](https://github.com/symfony/ux/issues/new/choose).
+
+Please provide as much information as possible,
+and remember to follow our [Code of Conduct](https://symfony.com/doc/current/contributing/code_of_conduct/index.html)
+as well, to ensure a friendly environment for all contributors.
+
+## Contributing to the code and documentation
+
+Thanks for your interest in contributing to Symfony UX! Here are some guidelines to help you get started.
+
+### Forking the repository
+
+To contribute to Symfony UX, you need to [fork the **symfony/ux** repository](https://github.com/symfony/ux/fork) on GitHub.
+This will give you a copy of the code under your GitHub user account, read [the documentation "How to fork a repository"](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/fork-a-repo).
+
+After forking the repository, you can clone it to your local machine:
+
+```shell
+$ git clone git@github.com:<USERNAME>/symfony-ux.git symfony-ux
+$ cd symfony-ux
+# Add the upstream repository, to keep your fork up-to-date
+$ git remote add upstream git@github.com:symfony/ux.git
+```
+
+### Setting up the development environment
+
+To set up the development environment, you need the following tools:
+
+- [PHP](https://www.php.net/downloads.php) 8.1 or higher
+- [Composer](https://getcomposer.org/download/)
+- [Node.js](https://nodejs.org/en/download/package-manager) 22 or higher
+- [Yarn](https://yarnpkg.com/) 4 or higher
+
+With these tools installed, you can install the project dependencies:
+
+```shell
+$ composer install
+$ corepack enable && yarn install
+```
+
+### Linking Symfony UX packages to your project
+
+If you want to test your code in an existing project that uses Symfony UX packages,
+you can use the `link` utility provided in this Git repository (that you have to clone).
+
+This tool scans the `vendor/` directory of your project, finds Symfony UX packages it uses,
+and replaces them by symbolic links to the ones in the Git repository.
+
+```shell
+$ php link /path/to/your/project
+```
+
+### Working with PHP code
+
+Symfony UX follows Symfony [PHP coding standards](https://symfony.com/doc/current/contributing/code/standards.html)
+and [the Backward Compatibility Promise](https://symfony.com/doc/current/contributing/code/bc.html).
+
+When contributing, please make sure to follow these standards and to write tests for your code,
+runnable with `php vendor/bin/simple-phpunit`.
+
+### Working with assets
+
+Assets are specific to each Symfony UX package:
+  - They are located in the `assets/` directory of each package, and can be either TypeScript or CSS files, respectively compiled through Rollup and PostCSS,
+  - Assets are mentioned in the `package.json` file of each package,
+  - Assets **must be** compiled before committing changes,
+  - Assets **must be** compatible with the [Symfony AssetMapper](https://symfony.com/doc/current/frontend/asset_mapper.html) and [Symfony Webpack Encore](https://symfony.com/doc/current/frontend/encore/index.html).
+
+To help you with assets, you can run the following commands in a specific package directory (e.g., `src/Map/assets/`):
+  - `yarn run build`: build (compile) assets from the package,
+  - `yarn run watch`: watch for modifications and rebuild assets from the package,
+  - `yarn run test`: run the tests from the package,
+  - `yarn run lint`: lint assets from the package,
+  - `yarn run format`: format assets from the package.
+
+Thanks to [Yarn Workspaces](https://yarnpkg.com/features/workspaces), you can also run these commands from the root directory of the project:
+  - `yarn run build`: build (compile) assets from **all** packages,
+  - `yarn run test`: run the tests from **all** packages,
+  - `yarn run lint`: lint assets from **all** packages,
+  - `yarn run format`: format assets from **all** packages,
+
+## Useful Git commands
+
+1. To keep your fork up-to-date with the upstream repository and `2.x` branch, you can run the following commands:
+```shell
+$ git checkout 2.x && \
+  git fetch upstream && \
+  git rebase upstream/2.x && \
+  git push origin 2.x
+```
+
+2. To rebase your branch on top of the `2.x` branch, you can run the following commands:
+```shell
+$ git checkout my-feature-branch && \
+  git rebase upstream/2.x && \
+  git push -u origin my-feature-branch
+```

README.md

@@ -50,18 +50,7 @@ Help Symfony by [sponsoring][3] its development!
 
 ## Contributing
 
-If you want to test your code in an existing project that uses Symfony UX packages,
-you can use the `link` utility provided in this Git repository (that you have to clone).
-This tool scans the `vendor/` directory of your project, finds Symfony UX packages it uses,
-and replaces them by symbolic links to the ones in the Git repository.
-
-```shell
-# Install required dependencies
-$ composer install
-
-# And link Symfony UX packages to your project
-$ php link /path/to/your/project
-```
+Thank you for considering contributing to Symfony UX! You can find the [contribution guide here](CONTRIBUTING.md).
 
 [1]: https://symfony.com/backers
 [2]: https://mercure.rocks