DOC: Link to CONTRIBUTING.md in README.md (py-pdf#2232)

Author: mp3403

README.md

@@ -63,6 +63,7 @@ For questions and answers, visit
 
 Maintaining pypdf is a collaborative effort. You can support the project by
 writing documentation, helping to narrow down issues, and submitting code.
+See the [CONTRIBUTING.md](https://github.com/py-pdf/pypdf/blob/main/CONTRIBUTING.md) file for more information.
 
 ### Q&A