- Add animationSpeed() method to HasIconAnimation trait
- Add speed parameter to spin() and pulse() shortcuts
- Support CSS duration format (e.g., '0.5s', '2s', '500ms')
- Default speeds: spin=1s, pulse=2s
- Add 6 new tests for animation speed functionality
- Update README with speed control documentation

Examples:
  ->spin('0.5s')           // Fast spin
  ->pulse('3s')            // Slow pulse
  ->spin()->animationSpeed('0.3s')  // Set speed separately