docs: add comment about host network to compose example

docker-compose.yml

@@ -9,6 +9,9 @@ services:
     volumes:
       - /var/run/docker.sock:/tmp/docker.sock:ro
 
+    # if you want to proxy based on host ports, you'll want to use the host network
+    # network_mode: "host"
+
   whoami:
     image: jwilder/whoami
     environment: