Use julia-format action

[JoshuaLampert]

Use https://github.com/julia-actions/julia-format to automatically suggest format changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.59%. Comparing base (4cda280) to head (3ccd68b).
Report is 23 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #69   +/-   ##
=======================================
  Coverage   98.59%   98.59%           
=======================================
  Files          40       40           
  Lines        1137     1137           
=======================================
  Hits         1121     1121           
  Misses         16       16           

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[JoshuaLampert]

Note to myself: The suggestions don't work for PRs from a fork, but they will still show up as warnings. So this is still better than before.