v0.0.8

Update version to 0.0.8 and refactor asset management in Gapless library

- Changed asset handling in GaplessEvent to introduce Started and Finished events for better clarity in playback state transitions.
- Updated GaplessPlayer and PlaylistManager to utilize MediaSlotData for managing current and preload assets, enhancing state management.
- Refactored MediaSlot and MediaSlotManager to accommodate the new slot data structure, improving the UI's responsiveness to asset changes.
- Adjusted unit tests to reflect changes in asset management and ensure correct behavior.