Add changelog

Signed-off-by: bowenlan-amzn <bowenlan23@gmail.com>

Author: bowenlan-amzn

CHANGELOG.md

@@ -30,6 +30,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Introduce framework for auxiliary transports and an experimental gRPC transport plugin ([#16534](https://github.com/opensearch-project/OpenSearch/pull/16534))
 - 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/))
+- 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))