Add changelog entry

Author: linuxdaemon

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Add Python 3.8 to testing matrix
 - Add support for channel keys (#95)
+- Officially support channel keys across the whole bot
 ### Changed
 - Refactor tests to remove dependency on mock library
 - Change link_announcer.py to only warn on connection errors