show method
Display this on top of the application.
Set fullScreenContentCallback before calling this method to be
notified of events that occur when showing the ad.
onUserEarnedReward
will be invoked when the user earns a reward.
Implementation
Future<void> show({required OnUserEarnedRewardCallback onUserEarnedReward}) {
onUserEarnedRewardCallback = onUserEarnedReward;
return instanceManager.showAdWithoutView(this);
}