ddns: remove ipv6 nameservers, support custom nameservers (#439)

resource/template/dashboard-default/setting.html

@@ -53,6 +53,10 @@
                 <label>{{tr "PanelServerDomainAndIP"}}</label>
                 <input type="text" name="GRPCHost" placeholder="" value="{{.Conf.GRPCHost}}">
             </div>
+            <div class="field">
+                <label>{{tr "CustomNameservers"}}</label>
+                <input type="text" name="CustomNameservers" placeholder="" value="{{.Conf.DNSServers}}">
+            </div>
             <div class="field">
                 <label>{{tr "IPChangeAlert"}}</label>
             </div>