Automated versioning and micro version releases

[tbenthompson]

It would be nice to just automatically increment the micro version number and release a new PyPI version every time we merge a green PR and then the main branch CI passes.

modal-client seems to have a good set up for this: https://github.com/modal-labs/modal-client/blob/main/.github/workflows/ci-cd.yml

I've used setuptools-scm for this some in the past.