Switch to new event system (#9)

* `SignalEvents` and `synchronized` mode for `EventsListenable`

* cascade syntax

* clean up

* `RoomEvents`

* `ParticipantEvents`

* all events implemented

* make it compile with M1 macs

* dispose logic

* cleaner connect logic

* ask to publish

* fix initial EngineTrackAddedEvent glitch

* fix unpublishTrack bug

* clean up

* better events docs

* organize event types

* clean up

* cleaner wait logic

* wait for event instead of using Completer

* notifyListeners

lib/src/utils.dart

@@ -1,25 +1,11 @@
-//
-//
-//
-
 import 'dart:async';
 
 import 'package:flutter_webrtc/flutter_webrtc.dart' as rtc;
 
+import 'extensions.dart';
 import 'options.dart';
 import 'track/options.dart';
-
-enum ProtocolVersion {
-  protocol2,
-  protocol3,
-}
-
-extension ProtocolVersionExt on ProtocolVersion {
-  String toStringValue() => {
-        ProtocolVersion.protocol2: '2',
-        ProtocolVersion.protocol3: '3',
-      }[this]!;
-}
+import 'types.dart';
 
 extension UriExt on Uri {
   bool get isSecureScheme => ['https', 'wss'].contains(scheme);