Adding ChangeLog.md

Signed-off-by: gashutos <gashutos@amazon.com>

CHANGELOG.md

@@ -104,6 +104,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Introduce full support for searchable snapshots ([#5087](https://github.com/opensearch-project/OpenSearch/issues/5087))
 - Introduce full support for Segment Replication ([#5147](https://github.com/opensearch-project/OpenSearch/issues/5147))
 - [Remote Store] Add support for enabling Remote Store at Cluster level by default. ([#6932](https://github.com/opensearch-project/OpenSearch/pull/6932))
+- Time series based workload desc order optimization through reverse segment read. ([#7244](https://github.com/opensearch-project/OpenSearch/pull/7244))
 
 ### Dependencies
 - Bump `org.apache.logging.log4j:log4j-core` from 2.18.0 to 2.20.0 ([#6490](https://github.com/opensearch-project/OpenSearch/pull/6490))
@@ -146,4 +147,4 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Security
 
 [Unreleased 3.0]: https://github.com/opensearch-project/OpenSearch/compare/2.x...HEAD
-[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.5...2.x
+[Unreleased 2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.5...2.x