Initial Release

implement video caching and advanced track selection

• Add CacheManager to handle LRU disk caching and HLS pre-caching.
• Update XMediaConfig with CacheConfig, TrackSelectorConfig, and BandwidthConfig.
• Implement a shared BandwidthMeter in PlayerFactory for consistent quality selection across player instances.
• Expose caching and bandwidth estimation APIs in XMediaState.
• Update MediaSourceFactory to support cache-aware data sources.
• Enhance README with detailed features, installation guide, and usage examples.