docs: Add entry to changelog

CHANGELOG.md

@@ -7,6 +7,14 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0).
 
 ## Unreleased
 
+### Changed
+
+- Relaxed type of `get_route_name` argument to `HTTPConnection`. This allows
+  developers to use the `get_route_name` function for getting the name of
+  websocket routes as well. Thanks to [@pajowu](https://github.com/pajowu) for
+  proposing and implementing this change in
+  [#276](https://github.com/trallnag/prometheus-fastapi-instrumentator/pull/276).
+
 ### Removed
 
 - **BREAKING:** Dropped support for Python 3.7 which is has reached end-of-life.