Provide stub files for typing support

[Spenhouet]

Hug does not work well with static type checkers since it does not provide stub files. The falcon project is on their way to provide typing support: https://github.com/falconry/falcon/issues/1350

For now they created a separate project to provide typing stubs: https://github.com/CoreyCole/falcon-stubs They plan on integrating these into the main project.

Maybe hug could also provide typing support in the future?