Allow `interact` to use basic type hint annotations

[corranwebster]

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This lets interact use type annotation information to create widgets, as proposed in #3907. Since type annotations are used as a last resort, this should not change the behavior of any currently working code.

Work that is needed:

• [x] tests
• [x] update documentation
• [x] code style clean-up

Fixes #3907

[github-actions[bot]]

:point_left: Launch a binder notebook on branch corranwebster/ipywidgets/feat/interact-type-hints

[corranwebster]

I am assuming that the failures for Javascript-related stuff is not related to the changes I have made.

Also, I couldn't find a python style guide or flake8/black/isort config, so I'm assuming that reasonably clean code is good enough. If not, let me know and I will lint appropriately.

With those caveats I think this is ready for review.