Determines the next app ad to be shown and shows it via a showDialog
freq - sets the number of times the app must be opened to show the next ad.
If set to 0, an ad will be shown everytime the determineAndShowAd method is called
Initializes the package with a list of apps that you would like to advertise
Alternative is to use initializeWithUrl if you wish to fetch app via a public URL
Fetches a list of apps to be advertised from the URL (Get), set updateFreqDays to limit the
http calls. Ensure that the response matches the AppInfo model otherwise this will fail.
Alternative is to use initializeWithApps if you would like the pass the data in directly