Updated changelog with breaking change message

Author: thomaskrause

CHANGELOG.md

@@ -5,6 +5,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- :boom: Removed usage of the `smartstring` crate. This changes the interface of the
+  `AnnoKey` and `Component`/`AnnotationComponent` structs and is a **breaking
+  change**, but the new interface is actually easier to call because the
+  conversion to smart strings is not necessary any longer. The change also
+  increases performance for several queries in the test set by up to 30%.
+
 ## [3.8.3] - 2025-08-12
 
 ### Fixed