fix(types): Add new cacheEnabled prop to typescript prop type declarations (#335)

typings/index.d.ts

    */
   originWhitelist?: string[];
 
+  /**
+   * Boolean value that determines whether caching is enabled in the
+   * `WebView`. The default value is `true` - i.e. caching is *enabled by default*
+   */
+  cacheEnabled?: boolean,
+
   /**
    * Override the native component used to render the WebView. Enables a custom native
    * WebView which uses the same JavaScript as the original WebView.