docs(docker-compose): More _FIXME_ markers

docker-compose/examples/hashicorpvault/README.md

@@ -50,6 +50,7 @@ Copy images to target Docker host, that is assuming you deploy to a machine that
 
 ```
 source "${COMPOSE_ENV}"
+# FIXME Docker Hub image name with or without slash? FIXME
 copy-docker.sh 'vault:'"${VAULT_VERSION}" fully.qualified.domain.name
 ```