clean up project root

[theorashid]

Still more to go here. Questions:

• [ ] Do we need to edit any of the workflows following these changes?
• [ ] Do we need the .gitpod.yml file? What is it doing?
• [ ] Can we move the readthedocs.yaml to docs/?
• [ ] What is the .gitattributes file doing? It won't work currently and do we still need it
• [ ] Do we need the buildosx file?
• [ ] Is the codecov.yml file used?
• [ ] Should conftest.py be moved to tests/? Is it used?
• [ ] Can CONTRIBUTING.md and CODE_OF_CONDUCT.md be moved anywhere like docs/ or .github?

cc: @jessegrabowski @maresb