Mtx.AddEventListener

This method can be used to listen for events related to the incentivized advertising API

The addEventListener method takes two arguments, the event type, and a callback function:

Name	Type	Description
`event_type`	String	Type of event to listen for
`callback`	Function	Function to call when the event is triggered

The following event types are currently supported:

Name	Description
`adsAvailable`	Ads are now available, and `showIncentivizedAd` will work
`adsUnavailable`	Ads are not available, and `showIncentivizedAd` will fail
`adOpened`	An ad is being displayed
`adCompleted`	An ad has completed successfully, and the player should be rewarded
`adAbandoned`	Ad ad has been closed before completion, the player should not be rewarded