implemented tracks, local & remote participants

lib/src/track/local_audio_track.dart

@@ -0,0 +1,8 @@
+import 'package:flutter_webrtc/flutter_webrtc.dart';
+
+import '../proto/livekit_models.pb.dart';
+import 'track.dart';
+
+class LocalAudioTrack extends Track {
+  LocalAudioTrack(String name, MediaStreamTrack track) : super(TrackType.AUDIO, name, track);
+}