added custom types

bin/list-custom

@@ -0,0 +1,12 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use Martnet::DDNS;
+
+my $ddns = Martnet::DDNS->new();
+
+my @vh = $ddns->get('_custom');
+foreach my $i (sort {$a->{zone} cmp $b->{zone}} @vh) {
+    print $i->{zone}, ". master: ", $i->{master},"\n";
+}