Add 2.x version to CHANGELOG (#4297)

Signed-off-by: Kunal Kotwani <kkotwani@amazon.com>

Signed-off-by: Kunal Kotwani <kkotwani@amazon.com>
(cherry picked from commit 1bfabed)

CHANGELOG.md

@@ -17,5 +17,21 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ### Security
 
+## [2.x]
+### Added
+- Github workflow for changelog verification ([#4085](https://github.com/opensearch-project/OpenSearch/pull/4085))
+
+### Changed
+
+### Deprecated
+
+### Removed
+
+### Fixed
+- PR reference to checkout code for changelog verifier ([#4296](https://github.com/opensearch-project/OpenSearch/pull/4296))
+
+### Security
+
 
 [Unreleased]: https://github.com/opensearch-project/OpenSearch/compare/2.2.0...HEAD
+[2.x]: https://github.com/opensearch-project/OpenSearch/compare/2.2.0...2.x