pihole: add proxy entry

pihole/docker-compose/pihole/docker-compose.yaml

@@ -25,6 +25,12 @@ services:
       - NET_ADMIN # Required if you are using Pi-hole as your DHCP server, else not needed
     restart: unless-stopped
 
+    networks:
+      traefik_traefik:
+
+networks:
+  traefik_traefik:
+    external: true
 
 volumes:
   pihole: {}