[BLD] Add link to hotfix PR in action summary

[eculver]

Description of changes

When applying a hotfix, a PR gets generated. This PR is currently only in the output of the action, or can be found in the list of PRs. This adds a heading and a link to the PR in the action summary so that the developer can find it more easily.

Test plan

I manually linted the action code to make sure I didn't break anything obvious. I may still want to tweak the output that gets generated, but at this point, the PR link will be much more easy to spot.

[github-actions]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)