fix: use clearColor instead of systemBackgroundColor for visionOS (#125)

Author: okwasniewski

packages/react-native/Libraries/AppDelegate/RCTAppDelegate.mm

@@ -186,8 +186,11 @@ - (UIView *)createRootViewWithBridge:(RCTBridge *)bridge
 #endif
   UIView *rootView = RCTAppSetupDefaultRootView(bridge, moduleName, initProps, enableFabric);
 
+#if TARGET_OS_VISION
+  rootView.backgroundColor = [UIColor clearColor];
+#else
   rootView.backgroundColor = [UIColor systemBackgroundColor];
-
+#endif
   return rootView;
 }