Callback when isConnectedViaWiFiWithoutInternet changes

[camhart]

Is your feature request related to a problem? Please describe.
I need to monitor when isConnectedViaWiFiWithoutInternet changes (even when a mobile data connection is maintained). The whenConnected callback isn't called when isConnectedViaWiFiWithoutInternet changes, I assume due to the cellular connection being the one offering the internet access.

Describe the solution you'd like
A callback that's triggered when isConnectedViaWiFiWithoutInternet changes. It could make sense to trigger the callback on changes to any of the following:

var isConnectedViaCellular: Bool
var isConnectedViaWiFi: Bool
var isConnectedViaCellularWithoutInternet: Bool
var isConnectedViaWiFiWithoutInternet: Bool

Great library, thank you for building/maintaining it.