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 {