docs: add version 2.0.0 to changelog

Author: tksugimoto

CHANGELOG.md

@@ -5,7 +5,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
-[Unreleased]: https://github.com/lerna-stack/akka-entity-replication/compare/v1.0.0...master
+[Unreleased]: https://github.com/lerna-stack/akka-entity-replication/compare/v2.0.0...master
+
+
+## [v2.0.0] - 2021-07-16
+[v2.0.0]: https://github.com/lerna-stack/akka-entity-replication/compare/v1.0.0...v2.0.0
 
 ### Breaking Change