Add confirmation button for hero recruit screen

Unknown

Hi. Loving the game so far. Just one suggestion:

If you get a weird bit of lag, or, in my case, you're tired and accidentally brush the screen you may accidentally buy a pack you didn't mean to buy. Like last night when I meant to redeem my gamma token but accidentally bought a powered-up token I didn't need.

A simple second pop-up dialog box would go a long way.