feat: add onAdError event listener (#3381)

* feat: add onAdError event listener
* feat: remove onAdError event listener and use already existing
* feat: add ERROR event to docs

src/types/Ads.ts

@@ -63,6 +63,10 @@ export enum AdEvent {
    * Android only: Fires when the ad's duration changes.
    */
   DURATION_CHANGE = 'DURATION_CHANGE',
+  /**
+   * Fires when an error is encountered and the ad can't be played.
+   */
+  ERROR = 'ERROR',
   /**
    * Fires when the ad playhead crosses first quartile.
    */