Update Changelog

Author: stefanzweifel

CHANGELOG.md

@@ -5,9 +5,13 @@ 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).
 
-## [Unreleased](https://github.com/stefanzweifel/php-changelog-updater/compare/v0.4.1...HEAD)
+## [Unreleased](https://github.com/stefanzweifel/php-changelog-updater/compare/v1.0.0...HEAD)
 
 <!-- New Release notes will be placed here automatically -->
+## [v1.0.0](https://github.com/stefanzweifel/php-changelog-updater/compare/v0.4.1...v1.0.0) - 2021-08-14
+
+Release v1.0.0.
+
 ## [v0.4.1](https://github.com/stefanzweifel/php-changelog-updater/compare/v0.4.0...v0.4.1) - 2021-08-14
 
 ### Fixed