CI: move docs job into separate workflow

[fingolfin]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.83%. Comparing base (a8518af) to head (cef9619).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #12   +/-   ##
=======================================
  Coverage   89.83%   89.83%           
=======================================
  Files          12       12           
  Lines        1151     1151           
=======================================
  Hits         1034     1034           
  Misses        117      117           

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