docs(changelog): Add changelog for playground open-url in Expo

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antonis

CHANGELOG.md

@@ -6,6 +6,12 @@
 > make sure you follow our [migration guide](https://docs.sentry.io/platforms/react-native/migration/) first.
 <!-- prettier-ignore-end -->
 
+## Unreleased
+
+### Features
+
+- Enable "Open Sentry" button in Playground for Expo apps ([#5947](https://github.com/getsentry/sentry-react-native/pull/5947))
+
 ## 8.7.0
 
 ### Features