feat: implement WebRTC calls

Signed-off-by: TheOneWithTheBraid <the-one@with-the-braid.cf>

lib/utils/voip/user_media_manager.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/foundation.dart';
+
+import 'package:flutter_ringtone_player/flutter_ringtone_player.dart';
+
+class UserMediaManager {
+  factory UserMediaManager() {
+    return _instance;
+  }
+
+  UserMediaManager._internal();
+
+  static final UserMediaManager _instance = UserMediaManager._internal();
+
+  Future<void> startRingingTone() {
+    if (kIsWeb) {
+      throw 'Platform [web] not supported';
+    }
+    return FlutterRingtonePlayer.playRingtone(volume: 80);
+  }
+
+  Future<void> stopRingingTone() {
+    if (kIsWeb) {
+      throw 'Platform [web] not supported';
+    }
+    return FlutterRingtonePlayer.stop();
+  }
+}