fix: onScroll type definition properly

src/WebViewTypes.ts

   injectedJavaScriptBeforeContentLoaded?: string;
   mediaPlaybackRequiresUserAction?: boolean;
   messagingEnabled: boolean;
-  onScroll?: (event: NativeScrollEvent) => void;
+  onScroll?: (event: NativeSyntheticEvent<NativeScrollEvent>) => void;
   onLoadingError: (event: WebViewErrorEvent) => void;
   onLoadingFinish: (event: WebViewNavigationEvent) => void;
   onLoadingProgress: (event: WebViewProgressEvent) => void;
   /**
    * Function that is invoked when the `WebView` scrolls.
    */
-  onScroll?: (event: NativeScrollEvent) => void;
+  onScroll?: (event: NativeSyntheticEvent<NativeScrollEvent>) => void;
 
   /**
    * Function that is invoked when the `WebView` has finished loading.