Support currently active Python versions

[amureki]

Greetings dear fellows,

I noticed that according to the README, the current "officially supported" Python versions are 2.7 to 3.5.
This is far off from the current state of Python:
https://endoflife.date/python

Instead of supporting 2.7, which is long dead and has less installations than the modern versions, I'd suggest focusing on supporting 3.8-3.12 (at least for now) and closely monitoring the Python versions release cycle.

I am happy to contribute to this; however, I am blocked by not knowing the current testing and coverage state. I guess, #6 can greatly help over it.

Best,
Rust