Add support for Python 3.11

[hugovk]

What does this PR do?

Add support for Python 3.11 and test on CI.

Python 3.12 support is pending a new release of aiohttp, which should be coming soon: https://github.com/aio-libs/aiohttp/issues/7639#issuecomment-1746582318.

Python 2.7 is EOL since 2020-01-01 and no longer supported on GitHub Actions, so I've not been able to test it. I recommend dropping Python 2.7, and see it's being removed in https://github.com/pusher/pusher-http-python/pull/207, but I can also remove it in this PR or another if you like.

Plus some GitHub Actions config updates.

• [x] If you have changed dependencies, ensure both requirements.txt and setup.py have been updated

CHANGELOG

• [ADDED] Add support for Python 3.11

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you'd like this issue to stay open please leave a comment indicating how this issue is affecting you. Thank you.

[hugovk]

Python 3.11 was released in 2022.

Please test it to make sure other changes do not introduce regressions.

[hugovk]

Since this PR was opened, Python 3.12 and 3.13 have ben released, but closing this year-old PR due to lack of interest. But happy to re-open again if you like!