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

example/ios/Podfile.lock

@@ -8,11 +8,14 @@ PODS:
   - Libyuv (1703)
   - path_provider (0.0.1):
     - Flutter
+  - shared_preferences (0.0.1):
+    - Flutter
 
 DEPENDENCIES:
   - Flutter (from `Flutter`)
   - flutter_webrtc (from `.symlinks/plugins/flutter_webrtc/ios`)
   - path_provider (from `.symlinks/plugins/path_provider/ios`)
+  - shared_preferences (from `.symlinks/plugins/shared_preferences/ios`)
 
 SPEC REPOS:
   trunk:
@@ -26,6 +29,8 @@ EXTERNAL SOURCES:
     :path: ".symlinks/plugins/flutter_webrtc/ios"
   path_provider:
     :path: ".symlinks/plugins/path_provider/ios"
+  shared_preferences:
+    :path: ".symlinks/plugins/shared_preferences/ios"
 
 SPEC CHECKSUMS:
   Flutter: 434fef37c0980e73bb6479ef766c45957d4b510c
@@ -33,7 +38,8 @@ SPEC CHECKSUMS:
   GoogleWebRTC: b39a78c4f5cc6b0323415b9233db03a2faa7b0f0
   Libyuv: 5f79ced0ee66e60a612ca97de1e6ccacd187a437
   path_provider: abfe2b5c733d04e238b0d8691db0cfd63a27a93c
+  shared_preferences: af6bfa751691cdc24be3045c43ec037377ada40d
 
-PODFILE CHECKSUM: aafe91acc616949ddb318b77800a7f51bffa2a4c
+PODFILE CHECKSUM: 6055d9653e1011c0b3b671abb92cdea979357e63
 
-COCOAPODS: 1.10.2
+COCOAPODS: 1.10.1