Add PR title and labels workflows

[graycampbell]

Summary

• Updated which PR events trigger the CI workflow.
• Added PR Labels workflow which checks that a PR has at least one required label.
• Added PR Title workflow which checks that a PR has a valid title that adheres to the contributing guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.69%. Comparing base (52d53d7) to head (94d70cb).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #60   +/-   ##
=======================================
  Coverage   88.69%   88.69%           
=======================================
  Files          24       24           
  Lines         292      292           
=======================================
  Hits          259      259           
  Misses         33       33           

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