Update CONTRIBUTING.md with detailed guidelines

Expanded the contributing guide to include instructions for forking, pull requests, referencing issues, and distinguishing between Issues and Discussions. Added sections on code style (PEP8), testing requirements, and pull request approval process to improve clarity for contributors.

Author: rclune

CONTRIBUTING.md

@@ -1,7 +1,38 @@
 # Contributing to RFDpoly
+Thank you for helping RFDpoly grow! Please follow the
+guidelines below to ensure the consistency of the code
+and documentation quality.
+
+To contribute to RFDpoly - either through code or 
+documentation contributions - please fork the repository,
+make changes, and create a pull request (PR). The pull 
+request should have `main` as the base branch.
+
+If your PR is a result of an Issue or Discussion, make
+sure to mention it in your description. 
+
+## Issues vs. Discussions
+An issue should be opened if there is an issue with the 
+code or there is a request for a new feature. 
+
+The Discussions section should be used to answer questions
+about best practices, usage, etc. 
 
 ## Code Contributions
 
+### Code Style and Quality
+When contributing to the code base, please adhere to the [PEP8 style guide](https://peps.python.org/pep-0008/).
+
+### Tests
+Please write tests for any contributed code or append to 
+existing tests.
+
+### Approving and Merging Pull Requests
+Currently only the original developers and the Devel Team 
+at Rosetta Commons can approve and merge pull requests. PRs
+will be merged via a merge commit, so all commits from the 
+feature branch will be added to the base branch.
+
 ## Documentation Contributions
 
 To preview the changes you made to the documentation before making a Pull Request you will need to