MAINT - clean / update docs and setup

[Badr-MOUFAD]

• Fix typos
  • grammar mistakes
  • use Celer, not celer (as it was coined in the original paper)
• Update License (date)
• Enhance code quality in setup.py

[codecov-commenter]

Codecov Report

Merging #249 (a7836b5) into main (ad0b107) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #249   +/-   ##
=======================================
  Coverage   86.97%   86.97%           
=======================================
  Files          14       14           
  Lines         998      998           
  Branches      131      131           
=======================================
  Hits          868      868           
  Misses        100      100           
  Partials       30       30           

Flag	Coverage Δ
unittests	∅ <ø> (∅)

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[mathurinm]

Thanks @Badr-MOUFAD !