Add documentation and new constructor (pointer + size) for u8_buffer,…

[Alex-PLACET]

… add operator[] too

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.69%. Comparing base (bf3a430) to head (a165ac2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #357      +/-   ##
==========================================
+ Coverage   89.67%   89.69%   +0.02%     
==========================================
  Files          88       88              
  Lines        6622     6638      +16     
==========================================
+ Hits         5938     5954      +16     
  Misses        684      684              

Flag	Coverage Δ
unittests	89.69% <100.00%> (+0.02%)	⬆️

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