Update CHANGELOG.md

Author: quantizor

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 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).
 
-## [7.0.0](https://github.com/styled-components/jest-styled-components/compare/v6.3.1...v7.0.0)
+## [7.0.0](https://github.com/styled-components/jest-styled-components/compare/v6.3.1...v7.0.0) - 2020-01-13
 
 - styled-components v5 support, drops support for s-c versions below v5
 - ship `stylesheetSerializer` as a named export