feat: update unit title plugin

[KristinAoki]

This PR updates the unit title plugin to include all the elements that are part of the unit title, which include the following:

• Unit title
• Bookmark button
• Navigation buttons when left sidebar navigation is enabled

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.09%. Comparing base (f39a50e) to head (1a790ad).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1643   +/-   ##
=======================================
  Coverage   90.08%   90.09%           
=======================================
  Files         338      338           
  Lines        5782     5784    +2     
  Branches     1410     1410           
=======================================
+ Hits         5209     5211    +2     
  Misses        556      556           
  Partials       17       17           

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