Add method to flip image horizontally (around vertical axis)

[bivant]

trafficstars

Update the example project to have a button that triggers this function (in the top right corner of the screen as bottom bar is full)

[TimOliver]

Thanks a lot for the PR @bivant! Let me think about this one for a bit. By adding an extra parameter to all the delegates and callbacks, it might break compatibility for a lot of folks.

That might be necessary, but I'm wondering if we can make this a bit more non-obtrusive. Thanks!