[Doc] Add developer notes

[riedgar-ms]

Expand the CONTRIBUTING file to describe the basic developer setup. Since our workflows access some quite expensive resources, PRs have to be approved to run. This will let contributors get feedback faster.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.39%. Comparing base (c23c8b0) to head (40b12e0).

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #774      +/-   ##
==========================================
- Coverage   68.87%   62.39%   -6.49%     
==========================================
  Files          55       55              
  Lines        4071     4071              
==========================================
- Hits         2804     2540     -264     
- Misses       1267     1531     +264     

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[Harsha-Nori]

Thoughts on extending CONTRIBUTING.MD with this info instead of having a new top level file here?

[riedgar-ms]

Thoughts on extending CONTRIBUTING.MD with this info instead of having a new top level file here?

That's an option too. I thought about it, but the existing file was more 'legalese' than information on how to contribute. Happy to switch if you prefer.

[riedgar-ms]

@Harsha-Nori , I've moved everything into CONTRIBUTING. I've also added some notes about how to hook new models into the testing setup on the off chance that random people feel inspired to push to main.