Don't tell people to use :latest

onbuild/README.md

@@ -2,9 +2,16 @@
 
 If you base a Dockerfile on this image:
 
-    FROM quay.io/jupyterhub/jupyterhub-onbuild:latest
+    FROM quay.io/jupyterhub/jupyterhub-onbuild:4.0.2
     ...
 
 then your `jupyterhub_config.py` adjacent to your Dockerfile will be loaded into the image and used by JupyterHub.
 
-This is how the `jupyter/jupyterhub` docker image behaved prior to 0.6.
+> [!NOTE]
+> Inherit from a tag that corresponds to the version of JupyterHub you want to use.
+> See our [quay.io page](https://quay.io/repository/jupyterhub/jupyterhub?tab=tags) for the list of
+> available tags.
+
+> [!WARNING]
+> Automatically loading the `jupyterhub_config.py` file was the default behavior of the `quay.io/jupyterhub/jupyterhub`
+> image prior to `0.6`.