Provide concise documentation of cumulusci.yml `project` configuration options

[yippie]

Feature Type

I'm interested in functionality that solves a current problem or limitation in how CumulusCI works.

Does your feature request solve a current problem?

Trying to configure my project, I don't even know what options are available to me. How does config differ between 1GP, 2GP, 2GP unlocked, and unpackaged projects? What are the project options? How do I write a plan?

Some options are scattered to the wind around the documentation to be found by luck, some is nicely documented, and some clearly isn't documented at all yet is configured during project init. "See examples", like the built in cumulusci.yml is terrible documentation as that does not explain what things do or give me any clue if that is ALL of the options or just SOME or what values are allowed.

Describe the solution you'd like

I would like ALL configuration tags and options defined, with a brief description (even just one sentence) in https://cumulusci.readthedocs.io/en/stable/config.html

Describe alternatives you've considered

No response

Additional context

No response