Adopt MyPy for type checking

[evamaxfield]

Use Case

Please provide a use case to help us understand your request in context

As we add more code to the library, tests will largely ensure we aren't adding anything is breaking, but we should also check the documented types.

Solution

Please describe your ideal solution

Adopt mypy for static type checking and add to tox and CI workflows

Probably adopt Prefect's mypy base config as well.

[mypy]
ignore_missing_imports = True
disallow_untyped_defs = True
check_untyped_defs = True

There are bound to be some failures off the bat which is why we do this 🙂

Alternatives

Please describe any alternatives you've considered, even if you've dismissed them