As a developer, I want documentation to help me learn how to contribute to the WRES codebase

[HankHerr-NOAA]

Feel free to reword the title as needed. As discussed last week, we need documentation to help guide folks in contributing to the WRES. At a minimum, it should be something high-level to serve as an entry point into understanding the code base. It may not need to be much more than that; its unclear at this time.

The current developer wiki only discusses editing wikis:

https://github.com/NOAA-OWP/wres/wiki/Instructions-for-Developers

This ticket is about fleshing that out a bit more.

Hank