add contributing guide

Author: gaelfoppolo

CONTRIBUTING.md

@@ -0,0 +1,71 @@
+# Contributing to _SonarQube Plugin for Swift_
+
+The following is a set of guidelines for contributing to _SonarQube Plugin for Swift_ on GitHub.
+
+> Above all, thank you for your interest in the project and for taking the time to contribute! 👍
+
+## I want to report a problem or ask a question
+
+Before submitting a new GitHub issue, please make sure to
+
+- Check out the [documentation](https://github.com/Backelite/sonar-swift/tree/develop/docs).
+- Check out the README and especially the usage guide.
+- Search for [existing GitHub issues](https://github.com/Backelite/sonar-swift/issues).
+
+If the above doesn't help, please [submit an issue](https://github.com/Backelite/sonar-swift/issues) on GitHub and provide information about your setup (SonarQube version, etc.)
+
+**Note**: If you want to report a regression in *SonarQube Plugin for Swift* (something that has worked before, but broke with a new release), please mark your issue title as such using `[Regression] Your title here`. This enables us to quickly detect and fix regressions.
+
+## I want to contribute to _SonarQube Plugin for Swift_
+
+### Prerequisites
+
+To develop _SonarQube Plugin for Swift_, you will need to meet the prerequisites as specified in the [README](https://github.com/Backelite/sonar-swift#prerequisites).
+
+### Checking out the repository
+
+- Make sure you are on the *develop* branch: https://github.com/Backelite/sonar-swift/tree/develop
+- Click the “Fork” button in the upper right corner of repo
+- Clone your fork:
+    - `git clone https://github.com/<YOUR_GITHUB_USERNAME>/sonar-swift.git`
+    - Learn more about how to manage your fork: <https://help.github.com/articles/working-with-forks/>
+- Create a new branch to work on:
+    - `git checkout -b <YOUR_BRANCH_NAME>`
+    - A good name for a branch describes the thing you’ll be working on, e.g. `add-swiftlint-rules`, `fix-swift-lexer`, etc.
+
+That’s it! Now you’re ready to work on _SonarQube Plugin for Swift_.
+
+### Things to keep in mind
+
+- Please do not change the minimum SonarQube version
+- Always document new public methods and properties
+
+### Testing your local changes
+
+Before opening a pull request, please make sure your changes don't break things.
+
+- The project and the plugin should build without warnings
+- The [Swift Language Weather](https://github.com/JakeLin/SwiftLanguageWeather) project should run without issues
+
+### Submitting the PR
+
+When the coding is done and you’ve finished testing your changes, you are ready to submit the PR to the [main repo](https://github.com/Backelite/sonar-swift). Again, make sure you submit your PR to the *develop* branch: https://github.com/Backelite/sonar-swift/tree/develop
+
+Some best practices are:
+
+- Use a descriptive title
+- Link the issues that are related to your PR in the body
+
+## Code of Conduct
+
+Help us keep _SonarQube Plugin for Swift_ open and inclusive. Please read and follow our [Code of Conduct](CODE_OF_CONDUCT.md).
+
+## Above All, Thanks for Your Contributions
+
+Thank you for reading to the end, and for taking the time to contribute to the project! If you include the 🔑 emoji at the top of the body of your issue or pull request, we'll know that you've given this your full attention and are doing your best to help!
+
+## License
+
+This project is licensed under the terms of the GNU LGPL v3 license. See the [LICENSE](./LICENSE.md) file for more info.
+
+_These contribution guidelines were adapted from [_fastlane_](https://github.com/fastlane/fastlane) guides._

README.md

@@ -162,11 +162,10 @@ If you still have *run-sonar-swift.sh* file in each of your project (not recomme
 
 Thank you for your interest in the project! Contributions are welcome and appreciated.
 
-Make sure to read this guide before getting started:
+Make sure to read these guides before getting started:
 
 - [Code of Conduct](./CODE_OF_CONDUCT.md)
-
-When creating a pull request: always create it for the *develop* branch. 
+- [Contribution Guidelines](./CONTRIBUTING.md)
 
 ### License