add support for code coverage tracking

[reece]

e.g., https://about.codecov.io/blog/python-code-coverage-using-github-actions-and-codecov/

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[dylan-myome]

I can grab this, please expect an access request from codecov.io