Add “github” extra deps. to the “all” extra

[musicinmybrain]

What does this PR do?

Adds the dependencies for the github extra to the all extra. It looks like omitting these was an oversight rather than an intentional decision.

Fixes (no issue reported)

[codecov]

Codecov Report

Merging #715 (f0bff45) into main (d5a986c) will not change coverage.
Report is 1 commits behind head on main.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #715   +/-   ##
=======================================
  Coverage   91.50%   91.50%           
=======================================
  Files          17       17           
  Lines        1625     1625           
=======================================
  Hits         1487     1487           
  Misses        138      138           

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