Add missing Messagease functionality: tap to hide

[MilesBHuff]

If it's trivial for you to do, would you please consider adding an option that makes the top control key's tap action be to collapse the keyboard, like in Messagease?

I realize that newer versions of Android have added a way to hide the keyboard with the virtual button bar (which makes this feature redundant), but it's hard to undo 13 years of muscle memory saying that tapping the top control button hides the keyboard...

[MilesBHuff]

Duplicate of #232, whoops!