Add function for when front-card is mounted

[jcb121]

In my app I use a textField inside of a SwipeItem sometimes.

When autofocus: true is set, the keyboard opens automatically causing the cards to re-size. This is the expected behaviour, but if the card behind has a textField and the card infront does not, the keyboard is opened also.

Is there anyway from inside the SwipeItem to tell if it's the current item? or a callback that fires when it becomes the current item?

thanks, Jesse,