Support three-finger undo/redo gestures outside text fields

[nolanw]

https://twitter.com/featherless/status/1476043571874742272

This means 3-finger gestures will feel inconsistently supported by most iOS apps, which in turn means users will be less likely to trust it even if they have found it, which is all too bad because it actually is much nicer than shaking your phone :)

Can we make this better? Yes!

You can "force" 3-finger gestures to be enabled in your app using the following snippet:

let tf = UITextField()
view.addSubview(tf)
tf.becomeFirstResponder()
tf.resignFirstResponder()
tf.removeFromSuperview()

Note that the view needs to be attached to a window.