Adds changelog

Author: antonis

CHANGELOG.md

@@ -20,6 +20,7 @@
 - crashedLastRun now returns the correct value ([#4829](https://github.com/getsentry/sentry-react-native/pull/4829))
 - Use engine-specific promise rejection tracking ([#4826](https://github.com/getsentry/sentry-react-native/pull/4826))
 - Fixes Feedback Widget accessibility issue on iOS ([#4739](https://github.com/getsentry/sentry-react-native/pull/4739))
+- Report slow and frozen frames as app start span data ([#4865](https://github.com/getsentry/sentry-react-native/pull/4865))
 
 ### Dependencies