Simulcast, Screen sharing & Various improvements (#4)

* Respect `RTCIceTransportPolicy` enum and organize

* Simplify syntax where possible etc.

* Combine `VideoPreset` and `VideoPresets`

* Default values for `ConnectOptions`

* Build URI instead of String manipulation

* Slight modifications to Exception

* `LiveKitTheme` for example

* `VideoEncoding` class

* Organize imports

* First simulcast implementation

* Remove unnecessary try-catches

* Update Android settings

* Remember uri and token

* example improvements

* `fit` parameter for VideoTrackRenderer

* Simulcast option for example

* Pass `defaultPublishOptions`

* Show only `VideoQuality`

* Pass tests

* Better buildUri logic

* Named parameter to positional

* Explicit imports

* `VideoParameter` instead of `VideoPreset`

* Use `mediaTrack.getSettings` when possible

* Safer dispose logic

* Safer `PCTransport`

Update transport.dart

* Synchronized events for `SignalClient`

* Use logger instead of print

* Make example compile for iOS

* First screen share implementation

* Make example work with screen share

* Example improvement

* Code optimization

* Don't depend on web_socket_channel

* Fix: Unpublish track bug

* Show participant mute state & identity

* Update protos

* Remote mute/unmute

* iOS Background mode

* Separate `createCameraTrack` and `createScreenTrack`

* Clean up

* PB fix

* format

* Fix analyzer warning

* Android clean up

* Update README.md

* Clean up

lib/src/widget/video_track_renderer.dart

@@ -1,22 +1,24 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_webrtc/flutter_webrtc.dart';
 
-import '../track/video_track.dart';
 import '../track/local_video_track.dart';
+import '../track/video_track.dart';
 
 /// Widget that renders a [VideoTrack].
 class VideoTrackRenderer extends StatefulWidget {
   final VideoTrack track;
   final RTCVideoRenderer renderer;
+  final RTCVideoViewObjectFit fit;
 
-  VideoTrackRenderer(this.track)
-      : renderer = RTCVideoRenderer(),
+  VideoTrackRenderer(
+    this.track, {
+    this.fit = RTCVideoViewObjectFit.RTCVideoViewObjectFitContain,
+  })  : renderer = RTCVideoRenderer(),
         super(key: ValueKey(track.sid));
 
   @override
-  State<StatefulWidget> createState() {
-    return _VideoTrackRendererState();
-  }
+  State<StatefulWidget> createState() => _VideoTrackRendererState();
 }
 
 class _VideoTrackRendererState extends State<VideoTrackRenderer> {
@@ -63,6 +65,7 @@ class _VideoTrackRendererState extends State<VideoTrackRenderer> {
       _renderer,
       mirror: isLocal,
       filterQuality: FilterQuality.medium,
+      objectFit: widget.fit,
     );
   }
 }