Add note about docker version

README.md

@@ -16,6 +16,10 @@ Repo for practice task for Autonomic front-end recruitment.
 
 ### `wp-env`
 
+**Note** this will only work with newer versions of Docker, if `docker compose`
+gives `'compose' is not a docker command.` then either upgrade Docker or use
+another method.
+
 You can launch an instance of WordPress pre-installed with this theme using the `wp-env` tool.
 
 ```sh