Update CHANGELOG for v0.4.0

Added entry for v0.4.0 documenting:
- UNICODE and LOCALE collation support for == operator
- Fix for PyICU tests in CI

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: tobixen

CHANGELOG.md

@@ -5,6 +5,14 @@ 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).
 
+## [0.4.0] - 2025-11-26
+
+### Added
+- **UNICODE and LOCALE collation support for "==" operator**: The == operator now properly supports UNICODE and LOCALE collations using ICU sort key comparison. Previously only BINARY and CASE_INSENSITIVE collations were supported for exact match operations.
+
+### Fixed
+- PyICU-based tests now pass in CI environments where PyICU is installed
+
 ## [0.3.1] - 2025-11-26
 
 Some wheel files etc that shouldn't be in the repository has accidentally been added.  Either I've done some silly mistake while sleeping, or perhaps it was a mistake giving the AI access to my computer.