feat: add default= parameter to Actions

[rich-iannone]

This PR adds the default= parameter to the Actions class. This is helpful in that a common callable or string (or list of various strings/callables) only needs to be set once to be a trigger for all three threshold levels.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.03%. Comparing base (db801c8) to head (5e59906).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #126   +/-   ##
=======================================
  Coverage   99.03%   99.03%           
=======================================
  Files          17       17           
  Lines        3610     3619    +9     
=======================================
+ Hits         3575     3584    +9     
  Misses         35       35           

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