Unregister all hotkeys by default when the app terminates

[sindresorhus]

I can't think of any scenario where I wouldn't want the shortcuts to be unregistered. Could also be an option, but if so, I think it should still default to true.

I don't want this boilerplate in my code:

func applicationWillTerminate(_ aNotification: Notification) {
	HotKeyCenter.shared.unregisterAll()
}

[Econa77]

@sindresorhus Thanks for your suggestion👍Support this with #21