Add change log

Signed-off-by: Daniel Widdis <[email protected]>

CHANGELOG.md

@@ -1,22 +1,24 @@
-CHANGELOG
-
+# CHANGELOG
+All notable changes to this project are documented in this file.
 
 Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
 
-2.12.0 Initial Release
-## [Unreleased]
-### Added
-- Github workflow for changelog verification ([#440](https://github.com/opensearch-project/flow-framework/pull/440))
-
-### Changed
-
-### Deprecated
-
-### Removed
-
-### Fixed
-
-### Security
-
-
-[Unreleased]: https://github.com/opensearch-project/flow-framework/compare/2.x...HEAD
+## [Unreleased 3.0](https://github.com/opensearch-project/flow-framework/compare/2.x...HEAD)
+### Features
+### Enhancements
+### Bug Fixes
+### Infrastructure
+### Documentation
+### Maintenance
+### Refactoring
+
+## [Unreleased 2.x](https://github.com/opensearch-project/flow-framework/compare/2.12...2.x)
+### Features
+### Enhancements
+- Substitute REST path parameters in Workflow Steps ([#525](https://github.com/opensearch-project/flow-framework/pull/525))
+
+### Bug Fixes
+### Infrastructure
+### Documentation
+### Maintenance
+### Refactoring