added comment for port mapping

minio/docker-compose.yml

@@ -9,7 +9,7 @@ services:
       - ${MINIO_DATA}/data:/mnt/data
       - ./data/home:/home/data
     ports:
-      - ${PORT_MAPPING} 
+      - ${PORT_MAPPING} # s3, port 9000
     environment:
       MINIO_ACCESS_KEY: ${MINIO_ACCESS_KEY}
       MINIO_SECRET_KEY: ${MINIO_SECRET_KEY}