implemented tracks, local & remote participants

lib/src/track/video_track.dart

@@ -0,0 +1,17 @@
+import 'package:flutter_webrtc/flutter_webrtc.dart';
+
+import '../proto/livekit_models.pb.dart';
+import 'track.dart';
+
+class VideoTrack extends Track {
+  VideoTrack(String name, MediaStreamTrack mediaTrack)
+      : super(TrackType.VIDEO, name, mediaTrack);
+
+  // TODO: keep list of video renderers
+
+  @override
+  stop() {
+    super.stop();
+    // TODO: remove renderer
+  }
+}