Modernize for Swift 5.9+

Major updates:
- Swift Package Manager support
- Swift 5.9+ with @mainactor for thread safety
- Simplified API: push(), pop() shortcuts
- setViewControllers() for full stack control
- 17 unit tests
- Updated documentation

Breaking changes:
- Minimum macOS 12.0
- Removed CocoaPods support
- Delegate methods now optional with default implementations

Release 0.1.1

fix popToRoot issue

rename

Add LICENSE

swift 4.2 compatibility

add assets