Checks if the current player can subscribe to the game bot.
It makes an async call to the API, so the result isn't available immediately.
If they can subscribe, the playerCanSubscribeBot property is set to true
and this plugin will emit the cansubscribebot event.
If they cannot, i.e. it's not in the list of supported APIs, or the request
was rejected, it will emit a cansubscribebotfail event instead.
This Facebook Instant Games Plugin instance.