Development
Infrastructure updates for static type checking and doctest examples.
- Move project layout to `src/`, va 364
- Initial [doctests] support added, via 359
[doctests]: https://docs.python.org/3/library/doctest.html
- Initial [mypy] validation, via 359
[mypy]: https://github.com/python/mypy
- CI (tests, docs): Improve caching of python dependencies via `action/setup-python`'s v3/4's new
poetry caching, via 359
- CI (docs): Skip if no `PUBLISH` condition triggered, via 359
- CI: Remove `.pre-commit-config.yaml`, users should know enough to handle these things themselves.