Add official support for Python 3.11

[florisla]

Hi,

The recent PySide6 release 6.4.0.1 now supports Python 3.11 too.

Qtpy officially only supports 3.6 to 3.10 but not yet 3.11.

Here's the commit which added 3.10: 0056412 .

Thanks a lot for this amazing project!

[dalthviz]

Hi @florisla thank you for the feedback and your nice words! We will do this in a future release 👍

[CAM-Gerlach]

FYI, I've opened PR #392 to implement this.

[CAM-Gerlach]

@dalthviz Since this is only a CI/tests/metadata update, and the existing code in 2.3 is already 3.11-compatible with no changes, can we bump this to 2.3.1 so it can be merged more promptly? Otherwise, there could be regressions in 3.11 support or conflicts with the PR, and this allows us to benefit from the updates to our CIs (which is basically all the changes) right away.