update CHANGELOG.md

Author: ioigoume

CHANGELOG.md

@@ -6,11 +6,12 @@ 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).
 
 <!-- markdownlint-disable line-length -->
-## [Unreleased]
+## [v4.0.0] - 2023-12-21
 
 ### Added
 
-- Add style rules and logos for IdP d4science.
+- Add support for simplesamlphp twig
+- Supports simplesamlphp v2 or greater
 
 
 ## [v3.1.0](https://github.com/rciam/simplesamlphp-module-themevanilla/compare/v3.0.0...v3.1.0) - 2021-08-27