When using Nearby Swap: Warn if user has VPN active

Some VPNs, but not all have an option to allow local LAN traffic. If that option isn't on or it doesn't exist, local LAN connections won't work. So it looks like we need to warn the user about an active VPN. This is how we can find out easily:

    val connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
    val activeNetwork = connectivityManager.activeNetwork ?: return false
    val networkCapabilities = connectivityManager.getNetworkCapabilities(activeNetwork) ?: return false
    return networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_VPN)