Release v0.4.0 (#35)

* docs: Add CLAUDE.md with project guidelines

- Complete project structure overview
- Common commands and workflows
- Release process (always use ./scripts/release.sh)
- Architecture details and optimizations
- Linting, testing, and CI/CD guides
- Troubleshooting tips

This file provides context for Claude Code to work more effectively
with the project without repeating instructions.

* Add CHANGELOG.md for release tracking

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

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

* RELEASE: v0.4.0

This release updates:
- version.py: 0.3.4 → 0.4.0
- CHANGELOG.md: Added release section for v0.4.0

After merging this PR:
- publish.yml workflow will trigger automatically
- Package will be built and published to PyPI
- GitHub release will be created with tag v0.4.0

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

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

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: vilsonrodrigues

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.4.0] - 2025-12-03
+
 ## [0.3.4] - 2025-12-02
 
 ## [0.3.3] - 2025-12-02

src/msgspec_ext/version.py

@@ -1 +1 @@
-__version__ = "0.3.4"
+__version__ = "0.4.0"