Write up changelog for 0.4.0

Author: deimonn

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.4.0](https://github.com/deimonn/code-re2c/compare/v0.3.0...v0.4.0) - 2025-04-23
+
+### Added
+
+- Support for Swift
+
 ## [0.3.0](https://github.com/deimonn/code-re2c/compare/v0.2.1...v0.3.0) - 2025-01-26
 
 ### Added