chore(CHANGELOG): add changes since last release

Author: JKRhb

CHANGELOG.md

@@ -11,6 +11,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- Switched to the [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) format for new changelog entries ([#115](https://github.com/eclipse-thingweb/dart_wot/pull/115))
+- Adjusted the main example to also use HTTP and CoAP observe ([#101](https://github.com/eclipse-thingweb/dart_wot/pull/101))
+
 ### Deprecated
 
 ### Removed