Global shortcts window

[moshfeu]

I almost done to implement shortcut window to this great app.

If you want to take a look:

https://github.com/moshfeu/baritone

And the commit itself

moshfeu@4b66efd

If you want, I can send a pull request and you will finish the window.

reference to shortcuts docs:

https://github.com/electron/electron/blob/master/docs/api/global-shortcut.md

If not, that's OK too :)