Description of problem:
Example of AgentConfig manifest is missing the apiVersion, resulting in
./openshift-install agent create image --dir cluster-manifests/
ERROR failed to write asset (Agent Installer ISO) to disk: cannot generate ISO image due to configuration errors
FATAL failed to fetch Agent Installer ISO: failed to load asset "Agent Config": apiVersion: Required value: no version was provided

Document

It should be:

apiVersion: v1alpha1