chore: prepare release 0.3.0

Author: natterstefan

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented here. The format is based
 on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) and this project
 adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## Unreleased
+## 0.3.0 (2020-06-27)
 
 ## Features