Add Python 3.10 support

[neumann-nico]

Summary

This PR adds support for Python 3.10

I had a look at those Python 3.9 PRs:
#3441
#4896

Changes

Changes setup.py and CI to inlcude Python 3.10

Importance

Python 3.10 is the latest stable version of Python so it would be great to include it :)

Checklist

This PR:

• adds new tests (if appropriate)
• adds a change file in the changes/ directory (if appropriate)
• updates docstrings for any new functions or function arguments, including docs/outline.toml for API reference docs (if appropriate)

[marvin-robot]

Here I am, brain the size of a planet and they ask me to welcome you to Prefect.

So, welcome to the community @neumann-nico! 🎉 🎉

[zanieb]

Thank you so much for contributing! This looks good. It was missing one line to include the workflow in CircleCI, I pushed a commit to add it. Also, if you don't quote "3.10" in the GitHub Actions YAML it'll treat it as a decimal 3.1 and run tests on the wrong version.

[tpdorsey]

Docs part lgtm! Thanks

[neumann-nico]

Thank you for the correction!
It seems like the installation of typed-ast does not work on Windows with Python 3.10

[zanieb]

I've removed mypy from the dev requirements as it's not needed for the Windows tests and is pinned in the type-checking CI job.

Thanks again!