docs: add doctests

[d-v-b]

• fix: use informed rtd configuration
• docs: add doctests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.21%. Comparing base (f19f49a) to head (665d628).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #14   +/-   ##
=======================================
  Coverage   99.21%   99.21%           
=======================================
  Files          10       10           
  Lines         256      256           
=======================================
  Hits          254      254           
  Misses          2        2           

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[codspeed-hq]

Merging this PR will not alter performance

✅ 48 untouched benchmarks

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_{Comparing d-v-b:docs/add-doctests (665d628) with main (0e3b66d)}