Bad "kill process" keybinding on Linux (and possibly Windows)

The current keybinding to kill the script process is `ctrl-q`, which is conflicting with the "Quit" keybinding in Atom. So, trying to kill the script process quits Atom.

I don't know if `ctrl-q` was recently added to Atom, as it probably used to work for killing the script process. Either that, or the "Quit" keybinding is different on Windows.

`ctrl-c` won't work either (see https://github.com/rgbkrk/atom-script/issues/120), because it conflicts with copy.

I currently use `ctrl-alt-shift-b`, so adding `alt` to the usual "Run script" keybinding makes it "Kill script". However, this is a bit clumsy to use with one hand, so `ctrl-shift-k` might be better?