Drop Python 3.8 support

[TobiX]

This allows us to increase the setuptools version (to 77 for now) and we can apply some pyupgrade modernisations...

[codecov]

Codecov Report

❌ Patch coverage is 82.14286% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.96%. Comparing base (ca7838f) to head (6ef72fa).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
dosagelib/plugins/l.py	0.00%	3 Missing ⚠️
dosagelib/plugins/wlpcomics.py	33.33%	2 Missing ⚠️
dosagelib/comic.py	50.00%	1 Missing ⚠️
dosagelib/plugins/a.py	0.00%	1 Missing ⚠️
dosagelib/plugins/b.py	0.00%	1 Missing ⚠️
dosagelib/plugins/n.py	0.00%	1 Missing ⚠️
dosagelib/plugins/p.py	0.00%	1 Missing ⚠️
dosagelib/plugins/petitesymphony.py	75.00%	1 Missing ⚠️
dosagelib/plugins/t.py	0.00%	1 Missing ⚠️
dosagelib/plugins/w.py	0.00%	1 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #367      +/-   ##
==========================================
- Coverage   89.05%   88.96%   -0.10%     
==========================================
  Files          97       96       -1     
  Lines        7129     7069      -60     
  Branches     1154      443     -711     
==========================================
- Hits         6349     6289      -60     
  Misses        780      780              

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