Add language facet filter to document search (#1402)

[blms]

In this PR

Per #1402:

• Index all languages of translation footnotes (by name) per document
• Add Select facet filter form field type
• Use that facet to select languages of translation
• Disable form control unless "has translation" is checked

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.87%. Comparing base (957daf0) to head (5fca8e4).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1650   +/-   ##
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  Coverage    98.87%   98.87%           
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  Files          241      241           
  Lines        14941    14989   +48     
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+ Hits         14773    14821   +48     
  Misses         168      168