Add changelog

Author: xrmx

CHANGELOG.md

@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#4494](https://github.com/open-telemetry/opentelemetry-python/pull/4494))
 - Improve CI by cancelling stale runs and setting timeouts
   ([#4498](https://github.com/open-telemetry/opentelemetry-python/pull/4498))
+- Fix serialization of extended attributes for logs signal
+  ([#4342](https://github.com/open-telemetry/opentelemetry-python/pull/4342))
 
 ## Version 1.31.0/0.52b0 (2025-03-12)