chore: SPEC0 update (Python 3.12+)

[flying-sheep]

Also improve docs. before:

after:

[codspeed-hq]

CodSpeed Performance Report

Merging #140 will not alter performance

_{Comparing pa/py3.12 (7405cc3) with main (da8e85a)}

Summary

✅ 232 untouched

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 45.75%. Comparing base (da8e85a) to head (7405cc3).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fast_array_utils/stats/_utils.py	66.66%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (da8e85a) and HEAD (7405cc3). Click for more details.

HEAD has 5 uploads less than BASE

Flag	BASE (da8e85a)	HEAD (7405cc3)
	7	2

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #140       +/-   ##
===========================================
- Coverage   99.15%   45.75%   -53.41%     
===========================================
  Files          19       15        -4     
  Lines         473      365      -108     
===========================================
- Hits          469      167      -302     
- Misses          4      198      +194     

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