Add changes to changelog

Signed-off-by: Rishabh Maurya <rishabhmaurya05@gmail.com>

CHANGELOG.md

@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Add support for Azure Managed Identity in repository-azure ([#12423](https://github.com/opensearch-project/OpenSearch/issues/12423))
 - Add useCompoundFile index setting ([#13478](https://github.com/opensearch-project/OpenSearch/pull/13478))
 - Make outbound side of transport protocol dependent ([#13293](https://github.com/opensearch-project/OpenSearch/pull/13293))
+- Derived field object type support ([#13720](https://github.com/opensearch-project/OpenSearch/pull/13720))
 
 ### Dependencies
 - Bump `com.github.spullara.mustache.java:compiler` from 0.9.10 to 0.9.13 ([#13329](https://github.com/opensearch-project/OpenSearch/pull/13329), [#13559](https://github.com/opensearch-project/OpenSearch/pull/13559))