Technically this option only selects which camera to start the search at, but we tell the user that it selects the camera for simplicity.
By default, camera feed will not be shown to the user.
Config file is now stored under ~/.config in Linux, and %AppData%\Roaming in Windows. Custom prefix has been changed to %AppData%\Local\Facecam2D in Windows, instead of the improper %AppData%\Facecam2D. MacOS paths remain unchanged.
`fc2dconfig` will write a config file, and `fc2d` will read it.