chore: better typechecking by checking in source code for libs

As a follow up of https://github.com/microsoft/winml-cli/issues/775

Like
```
[[tool.mypy.overrides]]
module = ["optimum.*"]
follow_untyped_imports = true   # analyze optimum's source, honor its annotations

# type: ignore[misc]  # optimum base is untyped
```

It is valid for small libs