Update docker-compose.yml

Fixed the comment that said to keep the port on 80 as the default container port has changed to 8080. If left alone from an upgrade, this will prevent you from connecting to Dashy.

docker-compose.yml

@@ -20,7 +20,7 @@ services:
       # - /path/to/my-config.yml:/app/user-data/conf.yml
       # - /path/to/item-icons:/app/user-data/item-icons/
 
-    # Set port that web service will be served on. Keep container port as 80
+    # Set port that web service will be served on. Keep container port as 8080. Previously this was port 80 and has changed! 
     ports:
       - 4000:8080