Update CHANGELOG.md

Author: ash-t-luu

CHANGELOG.md

@@ -4,6 +4,9 @@ All notable changes to the "react-labyrinth" extension will be documented in thi
 
 Check [Keep a Changelog](http://keepachangelog.com/) for recommendations on how to structure this file.
 
-## [Unreleased]
+## [1.0.0]
 
-- Initial release
+- Initial release
+
+## [1.0.3]
+- Updated README.md in VS Code Marketplace Details section.