Add CI for localization updates (ref: pressbooks/ideas#283)

[greatislander]

This PR adds GitHub Actions to:

• Update the languages/pressbooks-lti-provider.pot localization source file in dev whenever a pull request is merged
• Update the languages/*.mo binary files in dev whenever their source languages/*.po files are updated

[codecov[bot]]

Codecov Report

Merging #110 into dev will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##                dev     #110   +/-   ##
=========================================
  Coverage     79.04%   79.04%           
  Complexity      327      327           
=========================================
  Files             9        9           
  Lines          1169     1169           
=========================================
  Hits            924      924           
  Misses          245      245           

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