Test on newer Python versions

[kkiesling]

Right now tests are only run on Python 3.6, 3.7, 3.8. The newest version available is 3.11 so we should test on 3.9, 3.10, and 3.11 as well. This should theoretically be a one line change in the CI yaml file unless there are features that are incompatible with the newer versions.

[MilosAtz]

Thanks Kalin! I think this makes sense, especially since GitHub Actions are free. I don't think there are any incompatible features that should affect execution on newer versions. Unfortunately, the earliest I can take a look at it this weekend, but feel free to initiate if it's pressing.