refactor: use system background color in rootView

@@ -44,7 +44,11 @@ static void InitializeFlipper(UIApplication *application) {
                                                    moduleName:@"NGPlay"
                                             initialProperties:nil];
   
+  if (@available(iOS 13.0, *)) {
+    rootView.backgroundColor = [UIColor systemBackgroundColor];
+  } else {
     rootView.backgroundColor = [[UIColor alloc] initWithRed:1.0f green:1.0f blue:1.0f alpha:1];
+  }
 
   self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
   UIViewController *rootViewController = [UIViewController new];