[Project Hygiene] Add a CONTRIBUTING.md document
What?
A CONTRIBUTING.md document is available in the project root.
Why?
A CONTRIBUTING.md document can help potential new contributors know where to start and how they can help the project out. This should be inclusive of coders and non-coders alike.
These are guidelines I agree with overall: https://contributing.md/how-to-build-contributing-md/. A few of these are already taken care of such as the Code of Conduct and others are lacking such as a defined coding convention and style guide.