I was playing with this demo in web and OSX, the "Z" key is actually a "Y" key on my keyboard.
So, i guess we need a way of detecting the keyboard locale and then remapping the displayed Key.
So, for my german keyboard, the "Z" text display shoudl say "Y".

https://en.wikipedia.org/wiki/German_keyboard_layout

https://github.com/hajimehoshi/ebiten/blob/master/examples/hsv/main.go#L67