fix(player): capture media screenshots

close #1077

lib/services/keyboard_shortcuts_service.dart

@@ -378,7 +378,7 @@ class KeyboardShortcutsService extends ChangeNotifier {
         onSkipMarker?.call();
         break;
       case 'screenshot':
-        unawaited(player.command(['screenshot', 'window']).then((_) => onScreenshot?.call()));
+        unawaited(player.command(['screenshot', 'subtitles']).then((_) => onScreenshot?.call()));
         break;
     }
   }

test/services/keyboard_shortcuts_service_test.dart

@@ -40,7 +40,7 @@ void main() {
 
     expect(result, KeyEventResult.handled);
     expect(player.commands, [
-      ['screenshot', 'window'],
+      ['screenshot', 'subtitles'],
     ]);
     expect(feedbackCount, 1);
   });