Update CHANGELOG.md
[0.3.0] 2021-04-15
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project aims to adhere to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+
+## [0.3.0] 2021-04-15
+
+### Added
+* Support ClickHouse Server protocol (#225) - Thanks @sundy-li
+* Support Helm chart for datafuse (#253) - Thanks @tlightsky
+* Support group-by aggregation (#296)
