checkpoint - participant & tracks initial stubs

lib/src/track/track.dart

@@ -4,3 +4,7 @@ class TrackDimension {
 
   TrackDimension(this.width, this.height);
 }
+
+class Track {
+  String? sid;
+}

lib/src/track/track_publication.dart

@@ -0,0 +1,31 @@
+import '../proto/livekit_models.pb.dart';
+import 'track.dart';
+
+class TrackPublication {
+  Track? track;
+  String name;
+  String sid;
+  TrackType kind;
+  bool muted = false;
+  bool simulcasted = false;
+  TrackDimension? dimension;
+
+  bool get isSubscribed => track != null;
+
+  TrackPublication({required this.sid, required this.name, required this.kind});
+
+  TrackPublication.fromInfo(TrackInfo info)
+      : sid = info.sid,
+        name = info.name,
+        kind = info.type {
+    _updateFromInfo(info);
+  }
+
+  _updateFromInfo(TrackInfo info) {
+    muted = info.muted;
+    simulcasted = info.simulcast;
+    if (info.type == TrackType.VIDEO) {
+      dimension = new TrackDimension(info.width, info.height);
+    }
+  }
+}