chore: Add breaking change category to release generator

[tvdeyen]

Summary

We want to mark some PRs as breaking change. For that we need a label and the category

Checklist

Check out our PR guidelines for more details.

The following are mandatory for all PRs:

• I agree that my PR will be published under the same license as Solidus.
• I have written a thorough PR description.
• I have kept my commits small and atomic.
• I have localized any and all user-facing strings that I added to the source code.
• I have used clear, explanatory commit messages.

The following are not always needed:

• 📖 I have updated the README to account for my changes.
• 📑 I have documented new code with YARD.
• 🛣️ I have opened a PR to update the guides.
• ✅ I have added automated tests to cover my changes.
• 📸 I have attached screenshots to demo visual changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.16%. Comparing base (1f5bf5c) to head (c12f481).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6552      +/-   ##
==========================================
+ Coverage   91.82%   92.16%   +0.33%     
==========================================
  Files         879     1037     +158     
  Lines       17772    21195    +3423     
==========================================
+ Hits        16320    19534    +3214     
- Misses       1452     1661     +209     

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