feat: audio output select for web. (#247)

* feat: audio output select for web.

* chore: Add comments for VideoTrackRenderer.

* update.

lib/src/support/platform.dart

@@ -1,7 +1,5 @@
 import 'dart:io';
 
-import 'package:meta/meta.dart';
-
 import 'platform/io.dart' if (dart.library.html) 'platform/web.dart';
 
 // Returns the current platform which works for both web and devices.
@@ -9,7 +7,6 @@ PlatformType lkPlatform() => lkPlatformImplementation();
 
 bool lkPlatformIs(PlatformType type) => lkPlatform() == type;
 
-@internal
 bool lkPlatformIsTest() => Platform.environment.containsKey('FLUTTER_TEST');
 
 enum PlatformType {

lib/src/track/remote/audio.dart

@@ -43,4 +43,8 @@ class RemoteAudioTrack extends RemoteTrack
     }
     return didStop;
   }
+
+  Future<void> setAudioOutput(String deviceId) async {
+    audio.setAudioOutput(getCid(), deviceId);
+  }
 }

lib/src/track/web/_audio_api.dart

@@ -7,3 +7,7 @@ void startAudio(String id, rtc.MediaStreamTrack stream) {
 void stopAudio(String id) {
   // do nothing
 }
+
+void setAudioOutput(String id, String deviceId) {
+  // do nothing
+}

lib/src/track/web/_audio_html.dart

@@ -51,3 +51,10 @@ html.DivElement findOrCreateAudioContainer() {
   html.document.body?.append(div);
   return div as html.DivElement;
 }
+
+void setAudioOutput(String id, String deviceId) {
+  final audioElement = html.document.getElementById(audioPrefix + id);
+  if (audioElement is html.AudioElement) {
+    audioElement.setSinkId(deviceId);
+  }
+}