Update CHANGELOG

Author: shepherd-l

OneSignalExample/Assets/OneSignal/CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Fixed
 - Additional instance of OneSignal error when calling OneSignal methods in Awake()
+- iOS Mac Catalyst build error: Use of undeclared identifier 'OneSignalLiveActivitiesManagerImpl'
 
 ## [5.1.6]
 ### Fixed