loadAd method
Implementation
Future<bool?> loadAd() {
_initAd();
_startListening();
_startListeningReward();
return Ads.instance.channelInterstitial.invokeMethod("loadInterstitialAd", <String, dynamic>{
'id': id,
'adSlotId': adSlotId,
'adParam': adParam.toJson(),
});
}