Add changelog

Signed-off-by: bowenlan-amzn <[email protected]>

CHANGELOG.md

@@ -31,6 +31,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Changes to support IP field in star tree indexing([#16641](https://github.com/opensearch-project/OpenSearch/pull/16641/))
 - Support object fields in star-tree index([#16728](https://github.com/opensearch-project/OpenSearch/pull/16728/))
 - Support searching from doc_value using termQueryCaseInsensitive/termQuery in flat_object/keyword field([#16974](https://github.com/opensearch-project/OpenSearch/pull/16974/))
+- Improve performance of the bitmap filtering([#16936](https://github.com/opensearch-project/OpenSearch/pull/16936/))
 
 ### Dependencies
 - Bump `com.google.cloud:google-cloud-core-http` from 2.23.0 to 2.47.0 ([#16504](https://github.com/opensearch-project/OpenSearch/pull/16504))