Allow specifying a network interface

[KempDewulf]

I would like a parameter to pick an interface to use with the ping.
On linux it would add the -I parameter to the command.

Maybe a helper function to fetch the available interfaces into a list?

[KempDewulf]

something like:

@override
  List<String> get params {
    var params = ['-O', '-n', '-W $timeout', '-i $interval', '-t $ttl'];
    if (count != null) params.add('-c $count');
    if (source != null) params.add('-I $interface');
    
    return params;
  }