Add RELEASE.md

[BenediktBurger]

ToDos:

• Fix it to use numbers instead of #. for counting
• Update with the experience of the conda release
• Add update of citation.cff to the workflow

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.04%. Comparing base (dcef98f) to head (175ec8c).
Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #79      +/-   ##
==========================================
+ Coverage   87.66%   89.04%   +1.37%     
==========================================
  Files          36       36              
  Lines        2903     2902       -1     
  Branches      355      355              
==========================================
+ Hits         2545     2584      +39     
+ Misses        298      267      -31     
+ Partials       60       51       -9     

Flag	Coverage Δ
unittests	89.04% <ø> (+1.37%)	⬆️

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