fix: add CONTRIBUTING doc and update README

CONTRIBUTING.md

@@ -0,0 +1,9 @@
+# Contributing
+
+Thanks for your interest in contributing to PayLink! Please take a moment to review this document **before submitting a pull request**.
+
+## Pull requests
+
+**Please ask first before starting work on any new features**
+
+It's never a fun experience to have your pull request declined after investing a lot of time and effort into a new feature. To avoid this from happening, we request that contributors create [a feature request](https://github.com/dlcastillop/paylink/discussions/new?category=ideas) to first discuss any significant new ideas.

README.md

@@ -403,4 +403,8 @@ Many thanks to [Manuel Ernesto](https://twitter.com/manuelernestog), [Yoannis S
 
 ## Contributions
 
-Suggestions and pull requests are welcomed!
+If you're interested in contributing to PayLink, please read our [contributing docs](https://github.com/dlcastillop/dlcastillop/blob/main/CONTRIBUTING.md) before submitting a pull request.
+
+## Support
+
+Don't forget to leave a star!