Add job to validate that PR base branch is develop

[calda]

This PR adds a GitHub actions job to validate that a PR's base branch is develop.

For example, on a PR targeting main:

and a PR targeting develop:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.56%. Comparing base (d352277) to head (1d9c50f).
Report is 13 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2070      +/-   ##
===========================================
- Coverage    95.58%   95.56%   -0.02%     
===========================================
  Files          141      141              
  Lines        26331    26331              
===========================================
- Hits         25168    25164       -4     
- Misses        1163     1167       +4     

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