PEP-561 & PEP-484 style type support

It would be really great to add type annotations to this module so that downstream consumers don't need to either disable it from their type checkers, or do their own limited-scope stubbing.

There's some indication that there's demand (other than mine) from this stackoverflow: https://stackoverflow.com/questions/57785471/why-does-mypy-think-library-imports-are-missing

I'm more than up for helping out with this is this something the maintainers are interested in, otherwise typeshed is a potential alternative (though keeping it inline would be better for maintainability by far!)

I searched the issues as best I could and I don't believe this is duplicate, so at the very least this can act as a good gauge for how many people are interested in this as a feature!

L’issue n’identifie ni le module, ni les tests, ni les points d’entrée qui doivent être modifiés. Commencer par déterminer quel module du SDK est concerné et confirmer comment ses métadonnées de package exposent les types, puis convenir avec les maintainers de l’étendue des annotations et de l’approche de validation. La tâche est terminée lorsque les vérificateurs de types en aval peuvent utiliser le module sans stubs ni exclusions locales.

Rédigé par le modèle d'indexation à partir du texte de l'issue.