Better audio management (#10)

* add audio_session package

* `AudioManager` initial design

* try to integrate audio manager

* configure audio session

* `DisposeAware`

disposing if already published causes exception.

* organize

* guard flutter_webrtc calls

* websocket async fix

* use `ConnectionState` instead of `_isClosed` and `isReconnecting`

* change create audio track defaults

* update protos

* protocol 3 speaker updates

* fix exception

* emit `RoomDisconnectedEvent` only once

* fix exception

* keep track of local / remote audio tracks

* explicit types

* manage track state

* re-structure audio management

* change defaults

* unpublish all

* use experimental build

* change defaults

* configuring is optional

* call native `RTCAudioSession.setConfiguration`

* defaults adjustment

* iOS only for now

* use lib 92.4515.07

* clean up

* revert audio options for now

* remove pod source

* rename apple related audio

* `createListener` method

* organize native audio

* `SpeakingChangedEvent` only on `Participant`

* refactoring

* fix ios compile

* fix configure audio only for iOS logic

* minor fix & clean up

* change dispose logic

* format protos

* fix unpublishTrack

* `createListener` into a mixin

* simplify

* use flutter_webrtc master

* unpublish for example

* update ios icon

* android icon

* web icon

* favicon

example/lib/pages/room.dart

@@ -1,6 +1,7 @@
 import 'dart:convert';
 import 'dart:math' as math;
 
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:livekit_client/livekit_client.dart';
@@ -25,7 +26,7 @@ class RoomPage extends StatefulWidget {
 class _RoomPageState extends State<RoomPage> {
   //
   List<Participant> participants = [];
-  late final _listener = EventsListener<RoomEvent>(widget.room.events);
+  late final EventsListener<RoomEvent> _listener = widget.room.createListener();
 
   @override
   void initState() {
@@ -48,7 +49,9 @@ class _RoomPageState extends State<RoomPage> {
   }
 
   void _setUpListeners() => _listener
-    ..on<RoomDisconnectedEvent>((_) => Navigator.pop(context))
+    ..on<RoomDisconnectedEvent>((_) async {
+      WidgetsBinding.instance?.addPostFrameCallback((timeStamp) => Navigator.pop(context));
+    })
     ..on<DataReceivedEvent>((event) {
       String decoded = 'Failed to decode';
       try {