Update type annotations, make Ward pass mypy, distribute type annotations via PEP561

[darrenburns]

Type annotations have been used for the purpose of improving IDE code assistance so far.

MyPy has not been run, and this means that Ward currently does not pass type checking.

We should update the type annotations to ensure Ward passes mypy.

After this, we can add a build step to check the annotations on CI, and distribute the annotations via PEP561.

[hukkin]

#265 is the first but not final step here

[hukkin]

The only thing that remains to be done now is the TODO: in pyproject.toml

ward/pyproject.toml

Line 98 in a4a0b7c

# TODO: Remove these lines and fix type-checker errors to gradually introduce mypy

I.e. a few private modules and tests are still not type checked.

[AABur]

@darrenburns, this issue has already been implemented a long time ago. However, it looks like it's time to close it.

[edmorley]

With pylance, I still get:

Type of "test" is partially unknown
  Type of "test" is "(description: str, *args: Unknown, tags: List[str] | None = None, **kwargs: Unknown) -> ((func: Unknown) -> (((*args: Unknown, **kwargs: Unknown) -> Unknown) | Unknown))"Pylance[reportUnknownVariableType](https://github.com/microsoft/pylance-release/blob/main/DIAGNOSTIC_SEVERITY_RULES.md#diagnostic-severity-rules)

For from ward import test.