ci: include rc testing steps in checkboxes with github release afterward

[zimeg]

Changelog

N/A - but hopes to keep releases confident 🎁

Summary

This PR adds a testing checklist to the release candidate PR for reviewers to review before merging 🔮

Preview

📸 No recent changes to share at this time!

Testing

Will follow up as needed! But steps are recommended now for RC PRs-

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.70%. Comparing base (fe126f0) to head (21a2ac9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #576      +/-   ##
==========================================
+ Coverage   71.65%   71.70%   +0.05%     
==========================================
  Files         226      226              
  Lines       19148    19148              
==========================================
+ Hits        13720    13730      +10     
+ Misses       4218     4214       -4     
+ Partials     1210     1204       -6     

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[mwbrooks]

✅ Check list for the win! ☑️

[zimeg]

• @mwbrooks Boxes deserve a check I claim! 🏁