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

pubspec.yaml

@@ -8,18 +8,36 @@ environment:
   flutter: ">=1.17.0"
 
 dependencies:
-  collection: ^1.15.0
-  fixnum: ^1.0.0
   flutter:
     sdk: flutter
-  flutter_webrtc: ^0.6.6
+
+  collection: ^1.15.0
+  fixnum: ^1.0.0
+
+  flutter_webrtc: ^0.6.7
+
   http: ^0.13.3
   logging: ^1.0.1
   protobuf: ^2.0.0
-  tuple: ^2.0.0
-  web_socket_channel: ^2.1.0
-  uuid: ^3.0.4
 
+  tuple: ^2.0.0
+  
+  uuid: ^3.0.4
+  synchronized: ^3.0.0
+  
+  # 
+  # protobuf:
+  #   git:
+  #     url: https://github.com/google/protobuf.dart.git
+  #     ref: master
+  #     path: protobuf/
+
+  #
+  # WebSocketChannel has design flaws
+  # https://github.com/dart-lang/web_socket_channel/issues/25
+  #
+  # web_socket_channel: ^2.1.0
+  
 dev_dependencies:
   flutter_test:
     sdk: flutter