show At Event
Indicates in which call to checkAndShow() the flow will be shown.
For example, if you want to show the flow in the onResume() of the main activity:
RateApp.showAtEvent = 1: In this case, the flow will be shown in the first call to onResume(), which is when the activity is launched.
RateApp.showAtEvent = 2: In this case, the flow will be shown in the second call to the activity's onResume().