Update changelog

Author: blueluna

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Rearrange LED display modules under the same root module and change their
   APIs to be more aligned with each other.
 - Add BLE Beacon demo.
+- Add a simple speaker demo for micro:bit V2.
 
 ## [0.10.1] - 2021-05-25