changelog: adds note about closing #11221

CHANGELOG.md

@@ -1,5 +1,8 @@
 # 5.5.0 (unreleased)
 
+### New Features
+* **Alerting**: Adds support for Google Hangouts Chat notifications [#11221](https://github.com/grafana/grafana/issues/11221), thx [@PatrickSchuster](https://github.com/PatrickSchuster)
+
 ### Minor
 
 * **Elasticsearch**: Add support for offset in date histogram aggregation [#12653](https://github.com/grafana/grafana/issues/12653), thx [@mattiarossi](https://github.com/mattiarossi)