Add note about commented code

Co-authored-by: Phil Ewels <[email protected]>

docker-compose.yml

@@ -91,6 +91,8 @@ services:
     environment:
       MINIO_ROOT_USER: minio  # access key
       MINIO_ROOT_PASSWORD: minioPassword  # secret key
+    # NOTE: Uncomment if you want to keep your data.
+    #             Mounts a folder into the container to make uploaded data persistent.
     # volumes:
     #   - type: bind
     #     source: ./minio-data