CHANGELOG: Prepare v0.3.0 (#23)

Author: mxinden

CHANGELOG.md

@@ -4,7 +4,7 @@ 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 adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [0.3.0] unreleased
+## [0.3.0]
 ### Added
 
 - Add `RunParameters::data_network_ip` for ease of finding the IP within the data network assigned to the instance. See [PR 22].