Add benchmarks

[attipaci]

The README now provides a section on representative benchmarks. And, you may run your own benchmarks with make benchmark.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.73%. Comparing base (7036bc4) to head (6bfc66f).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #117   +/-   ##
=======================================
  Coverage   99.73%   99.73%           
=======================================
  Files           8        8           
  Lines        3385     3385           
  Branches      649      649           
=======================================
  Hits         3376     3376           
  Partials        9        9           

Flag	Coverage Δ
unittests	99.73% <ø> (ø)

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