Create CONTRIBUTE.md

[mjmeans]

First draft of a how to contribute information file in the repo.

[bhj]

This is a good idea. It does need some editing for clarity (for example the "getting started" steps should be separated from general best practices instead of being all in one numbered list)

More importantly, it doesn't address the elephant in the room, namely contributions from LLMs made with minimal human oversight. I am still deciding how hard of a line to take on this.

[bhj]

Some references:

• https://github.com/cezaraugusto/github-template-guidelines/blob/master/.github/CONTRIBUTING.md
• https://github.com/auth0/open-source-template/blob/master/GENERAL-CONTRIBUTING.md
• https://github.com/nayafia/contributing-template/blob/master/CONTRIBUTING-template.md

Also I believe the file needs to be named CONTRIBUTING.md