Calendar view for events (and other modules with DateRanges association)

[didoda]

This introduces a calendar view in index for modules that have "DateRanges" association.

This uses fullcalendar/vue: https://fullcalendar.io/docs/vue

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.77%. Comparing base (0570807) to head (dcc4e8b).
⚠️ Report is 7 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             master    #1335    +/-   ##
==========================================
  Coverage     99.77%   99.77%            
- Complexity     1467     1502    +35     
==========================================
  Files           102      102            
  Lines          5736     5880   +144     
==========================================
+ Hits           5723     5867   +144     
  Misses           13       13            

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