Add changelog entry for legal boilerplate validation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: vaind

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 ## Unreleased
 
+### Features
+
+- Danger - Add legal boilerplate validation for external contributors ([#145](https://github.com/getsentry/github-workflows/pull/145))
+  - Verify that PRs from non-organization members include the required legal boilerplate from the PR template
+  - Show actionable markdown hints when the boilerplate is missing or doesn't match
+
 ### Fixes
 
 - Sentry-CLI integration test action - Accept chunked ProGuard uploads for compatibility with Sentry CLI 3.x ([#140](https://github.com/getsentry/github-workflows/pull/140))