Update CHANGELOG

CHANGELOG.md

 # Changelog
 
+## [0.15.11] - Unreleased
+
+* Catch errors in setup-apps.sh to allow nextcloud to start regardless of them,
+  and add a prometheus monitor and alert so that we may still be notified of
+  any problems.
+* Update nextcloud helm chart to v3.5.0.
+* Update rabbitmq to v11.10.0.
+
 ## [0.15.10] - 2023-02-08
 
 * Adapt test to changed Stackspin dashboard button label.