Add APD link to doc search on Arabic/JA query (#1697)

[blms]

In this PR

Per #1697:

• Generate a link to the Arabic Papyrology Database when Arabic or JA are entered in the document search query
• Generate a regex version of a JA-to-Arabic translation for this link, since APD is only in Arabic, and supports regex
• Show the link at the bottom of the search results if it exists

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.95%. Comparing base (2ed1825) to head (1bdaabc).
Report is 2 commits behind head on develop.

Additional details and impacted files

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##           develop    #1732   +/-   ##
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  Coverage    98.95%   98.95%           
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  Files          247      247           
  Lines        16133    16152   +19     
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+ Hits         15965    15984   +19     
  Misses         168      168