Add release date for 0.4.2

Author: dbanty

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).
 
-## 0.4.2 - Unreleased
+## 0.4.2 - 2020-06-13
 ### Additions
 - Support for responses with no content (#63 & #66). Thanks @acgray!
 - Support for custom string formats (#64 & #65). Thanks @acgray!