updating xylophone links

Author: TheMuellenator

README.md

@@ -80,7 +80,7 @@
 * [Flutter Packages](https://pub.dartlang.org/flutter)
 * [Guide to Using Flutter Packages](https://flutter.dev/docs/development/packages-and-plugins/using-packages)
 * [Luan Nico's Audioplayers Package](https://pub.dartlang.org/packages/audioplayers)
-* [AudioCache Documentation](https://github.com/luanpotter/audioplayers/blob/master/doc/audio_cache.md)
+* [AudioCache Documentation](https://github.com/bluefireteam/audioplayers/blob/master/packages/audioplayers/doc/audio_cache.md)
 * [DartPad Functions Exercise](https://dartpad.dartlang.org/4bf7549c820d1adb4be8673e92820e43)
 * [Xylophone Completed Project](https://github.com/londonappbrewery/Xylophone-Flutter-Completed)