chore: Update changelog with release date

Author: 0ffz

CHANGELOG.md

@@ -6,7 +6,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 This project does not fully adhere to [Semantic Versioning](https://semver.org/spec/v2.0.0.html) while under heavy
 development.
 
-## [Unreleased]
+## [0.4.0] - 2025-11-02
 
 ### Added