show cursor x,y coordinates

[nurpax]

gathering user feedback:

some folks want to see the current mouse x,y coordinates (in char coords, of course)

agreed that this is probably helpful to be able to position some other elements like sprites on the screen.

[Esshahn]

I never missed the coordinates, but I do have use for showing the char number like $122, that comes in handy when coding, e.g. collisions.

Could all fit in a status bar of the app or below the character selection maybe

[nurpax]

Already covered by #88, closing this one.