Features:
- Thumbnail embedding for audio/video downloads
- AtomicParsley integration for MP4/M4A cover art
- Improved dependency management
- Enhanced GitHub Actions workflows

Improvements:
- CI/CD workflow with automatic testing
- Dependabot dependency updates
- Better Issue/PR templates
- SHA256 checksum generation

Bug Fixes:
- Fixed thumbnail embedding codec compatibility
- Improved file merging detection
- Better error handling for external tools