Updated changelog to reflect recent changes

Author: vladbagmet

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+- Fields `partition` and `rerun_partition` are not expected in partial merge event payload.
+- Data structure under `data` key  of partial merge event payload can accept additional fields.
 
 
 ## [1.11.0] - 2023-12-07