Added option to Start Minimized

[ahalekelly]

No description provided.

[JdotCarver]

I implemented the change on my side, it works great.
And I can say it's a very welcome addition!
🙏

[Enyium]

I find this PR a little clearer than #98, so prefer it over the other one.

But I don't know what the difference between

self.main_window.startListening.emit()

and

self.key_listener.start()

is, which the two PRs differ in (order: other one, this one).