Add Python 3.10 support

[zundertj]

Python 3.10 has been released on Oct 4 (see https://www.python.org/downloads/release/python-3100/). I'm not an expert on the Python-Rust bindings being used, but it seems PyO3 / maturin support Python 3.10, so this seems feasible? Would be great to add 3.10 support, as most libraries support it by now.

[ritchie46]

The python ABI is stable since python 3.6. So it should work on python 3.10

[zundertj]

Ok, I was hitting an error on my local Python 3.10 venv, turns out the recent upgrade I did for pytest solved it (i.e. see pytest-dev/pytest#8539 (comment))