chore: Add action to warn about potentially risky PR changes

[kahest]

:scroll: Description

Implement a mechanism that automatically adds an "alert" comment to PRs if they include changes to files we think have higher potential to break things than others.

:bulb: Motivation and Context

same as https://github.com/getsentry/sentry-java/pull/3726

:green_heart: How did you test it?

✅ by adding the file-filter.yml introduced in this PR to the list of potentially risky changes and ensuring that an alert is shown

:pencil: Checklist

• [x] I reviewed the submitted code
• [ ] ~I added tests to verify the changes~
• [ ] ~I updated the docs if needed~
• [ ] ~No breaking changes~

:crystal_ball: Next steps

skip-changelog

[github-actions[bot]]

🚨 Detected changes in high risk code 🚨

High-risk code has higher potential to break the SDK and may be hard to test. To prevent severe bugs, apply the rollout process for releasing such changes and be extra careful when changing and reviewing these files:

• [ ] .github/file-filters.yml