Add initializer to `KeyboardShortcuts.Recorder` that accepts a binding

[sindresorhus]

This would let developers use the recorder for custom use-cases when they don't need everything that comes with the Name system. For example, support for local shortcuts.

import SwiftUI
import KeyboardShortcuts

struct SettingsScreen: View {
	@State private var shortcut: KeyboardShortcuts.Shortcut?

	var body: some View {
		Form {
			KeyboardShortcuts.Recorder("Toggle Unicorn Mode:", shortcut: $shortcut)
		}
	}
}

Also document how to use this to be able to use the recorder to record local shortcuts.