Add Python 3.12 => PEP 693

[hugovk]

Awaiting merge of python/peps#2648.

Plus some config and test updates.

[codecov]

Codecov Report

Merging #14 (e5f87e7) into main (31389d6) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #14   +/-   ##
=======================================
  Coverage   96.75%   96.75%           
=======================================
  Files           4        4           
  Lines         185      185           
=======================================
  Hits          179      179           
  Misses          6        6           

Flag	Coverage Δ
GHA_Ubuntu	96.75% <100.00%> (ø)
GHA_Windows	96.75% <100.00%> (ø)
GHA_macOS	96.75% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pepotron/__init__.py	94.36% <ø> (ø)
tests/test_cache.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 31389d6...e5f87e7. Read the comment docs.