adding ovpn_listclients script

docs/clients.md

@@ -9,6 +9,12 @@ The [`ovpn_getclient`](/bin/ovpn_getclient) can produce two different versions o
 
 Note that some client software might be picky about which configuration format it accepts.
 
+## Client List
+
+See an overview of the configured clients, including revokation status:
+
+    docker run --rm -it --volumes-from $OVPN_DATA kylemanna/openvpn ovpn_listclients
+
 ## Batch Mode
 
 If you have more than a few clients, you will want to generate and update your client configuration in batch. For this task the script [`ovpn_getclient_all`](/bin/ovpn_getclient_all) was written, which writes out the configuration for each client to a separate directory called `clients/$cn`.