Updating changelog for "2.2.0".

Author: cyrilverloop

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).
 
-## [Unreleased]
+## [2.2.0] - 2022-02-10
 ### Added
 - Tests for "Conway sequence".
 - Tests for "The gift".