Update changelog

Signed-off-by: Aleksandr Tuliakov <[email protected]>

Author: MrChaos1993

CHANGELOG.md

@@ -5,6 +5,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ## [Unreleased]
 
 ### Added
+- Added `target_index_settings` to `Index Rollups API` from `index-management` plugin ([#822](https://github.com/opensearch-project/opensearch-api-specification/pull/822))
 - Added `aggs` alias for nested aggregations ([#818](https://github.com/opensearch-project/opensearch-api-specification/pull/818))
 - Added API specs for query groups lifecycle APIs ([#649](https://github.com/opensearch-project/opensearch-api-specification/pull/649))
 - Added Python and Ruby spec validators ([#646](https://github.com/opensearch-project/opensearch-api-specification/pull/646))