feat(websub) add content types

[danaivach]

Closes #53 by updating handleNotificationSending() and handleActionNotificationSending()

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.30%. Comparing base (27ebe3e) to head (efafe63).
Report is 375 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #54      +/-   ##
============================================
+ Coverage     75.27%   77.30%   +2.03%     
- Complexity      391      525     +134     
============================================
  Files            35       47      +12     
  Lines          2208     3208    +1000     
  Branches         75      132      +57     
============================================
+ Hits           1662     2480     +818     
- Misses          498      647     +149     
- Partials         48       81      +33     

Flag	Coverage Δ
unittests	77.30% <100.00%> (+2.03%)	⬆️

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[KaiTries]

looks good to me