Add Windows key to key_shortcut

I'd like to create a shortcut WIN+SHIFT+LEFT_ARROW to move my windows from one screen to the other. But it looks like the Windows key isn't supported? Any way to add? Thank you!

I also noticed there's no Fn/Function key. I was going to try to make an Fn+F7 shortcut to play/pause videos.

I don't currently have time to add new features to the project, but pull requests are always welcomed.