updated type for ViewManagerName

js/WebView.android.js

     );
   }
 
-  getViewManagerConfig = viewManagerName => {
+  getViewManagerConfig = (viewManagerName: string) => {
     if (!UIManager.getViewManagerConfig) {
       return UIManager[viewManagerName];
     }

js/WebView.ios.js

     );
   }
 
-  _getViewManagerConfig = viewManagerName => {
+  _getViewManagerConfig = (viewManagerName: string) => {
     if (!UIManager.getViewManagerConfig) {
       return UIManager[viewManagerName];
     }