Update CHANGELOG.

Author: Dallas62

.github/ISSUE_TEMPLATE/bug_report.md

@@ -50,4 +50,5 @@ Describe what you expected to happen:
 
 <!--
  Please add minimal runnable repro as explained above so that the bug can be tested in isolation.
+ Use the example project to reproduce it.
 -->

CHANGELOG.md

@@ -10,6 +10,8 @@ This project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html
 
 ### Features
 
+- Add support for specifying a delegate FirebaseMessagingService [#1589](https://github.com/zo0r/react-native-push-notification/pull/1589)
+
 ### Fixed