Pocket Clicker — proof of concept Game Boy "game"

[Araq]

Welcome and thank you for this report! I'm always eager to support `os:any` (as 
opposed to `os:standalone`) as Nim is just easier to use when not restricted to 
a subset. The IO operations should be gone with `--define:nimPreviewSlimSystem` 
but I'm sure some bug reports / pull requests will be helpful to make things 
easier on exotic platforms.