finish up CI configuration

[jmartin-sul]

blocked by #12, which provides initial CI setup.

besides specs (covered in #12), it'd be good to:

• [ ] lint (using ruff? i think that's what @edsu has been using? in the past we've also used flake8 and ruff, i think)
• [ ] type checking? mypy has been easy enough to setup, and pretty unobtrusive, and sometimes helpful in detecting issues, but we don't have super consistent policies about type checking our projects. (https://github.com/LD4P/ils-middleware is an example of mypy in one of our apps; https://github.com/sul-dlss/dlme-airflow was also, but it seems to have been partially but not entirely removed in a recent package manager switch)