Add type hints

[domdfcoding]

What are your thoughts on adding type hints (or standalone type stubs)? There's a PR for adding them to appdirs (ActiveState/appdirs#75), but it seems to have stalled. It's a feature I'd like, and I'd consider switching to platformdirs if it had them.

The hints for the function signatures are really simple: Optional[str] or bool for the arguments and str for the return type.

Happy to submit a PR

[gaborbernat]

We'll accept once we drop Python3.5 😊

[ofek]

Let's do that when we drop Python 2

[gaborbernat]

3.5 + 2 will go together 👍

[gaborbernat]

virtualenv released with platformdirs https://pypi.org/project/virtualenv/20.5.0/