Add CONTRIBUTING file

CONTRIBUTING.md

@@ -0,0 +1,14 @@
+## Raising a Bug
+While raising a bug, please provide:
+* Version of the SonarQube platform
+* Version of the CSS / SCSS / Less plugin
+* Log file of the analysis
+* Source code to reproduce the error
+
+## Contributing
+Any contribution is more than welcome!
+
+You feel like:
+* Adding a new check? Just [open an issue](https://github.com/racodond/sonar-css-plugin/issues/new) to discuss the value of your check. Once validated, code, don't forget to add a lot of unit tests and open a PR.
+* Maintaining the [stylelint / SonarQube rule mapping](https://github.com/racodond/sonar-css-plugin/blob/master/doc/stylelint-sonarqube-rule-mapping.md)? Just open a PR 
+* Fixing some bugs or improving existing checks? Just open a PR.

README.md

@@ -60,15 +60,6 @@ If your custom checks may benefit the community, feel free to create a pull requ
 You're thinking of new checks that may benefit the community but don't have the time or the skills to write them? Feel free to create an [issue](https://github.com/racodond/sonar-css-plugin/issues) for your checks to be taken under consideration.
 
 
-## Contributing
-Any contribution is more than welcome!
-
-You feel like:
-* Adding a new check? Just [open an issue](https://github.com/racodond/sonar-css-plugin/issues/new) to discuss the value of your check. Once validated, code, don't forget to add a lot of unit tests and open a PR.
-* Maintaining the [stylelint / SonarQube rule mapping](https://github.com/racodond/sonar-css-plugin/blob/master/doc/stylelint-sonarqube-rule-mapping.md)? Just open a PR 
-* Fixing some bugs or improving existing checks? Just open a PR.
-
-
 ## Metrics
 
 ### Functions