Redo boilerplate

[ewjoachim]

• Switch to poetry
• Switch to pre-commits
• Switch to scripts folder
• Remove tox
• Auto-release on GH Actions with release-drafter
• Add readthedocs CI

Successful PR Checklist:

• Tests
• Documentation (optionally: run spell checking)
• Had a good time contributing? (feel free to give some feedback)

[codecov]

Codecov Report

Merging #97 (77f2a8b) into master (d1b3ae3) will increase coverage by 14.53%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master      #97       +/-   ##
===========================================
+ Coverage   76.75%   91.29%   +14.53%     
===========================================
  Files          15       15               
  Lines         654      655        +1     
  Branches       83       83               
===========================================
+ Hits          502      598       +96     
+ Misses        145       47       -98     
- Partials        7       10        +3     

Flag	Coverage Δ
matrix.coverage-flag	?

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Impacted Files	Coverage Δ
septentrion/versions.py	100.00% <0.00%> (ø)
septentrion/configuration.py	97.91% <0.00%> (+11.45%)	⬆️
septentrion/migration.py	86.31% <0.00%> (+17.89%)	⬆️
septentrion/__main__.py	33.33% <0.00%> (+33.33%)	⬆️
septentrion/cli.py	90.41% <0.00%> (+90.41%)	⬆️

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[mgu]

🎉