This is a clone of the work done here on the openldap container: https://github.com/osixia/docker-openldap/tree/stable/example/extend-osixia-openldap
I have just created my own bootstrapped schema for easy use and testing.
If you want to use the pre-configured docker image directly you can find it here: https://hub.docker.com/r/johnowebb/openldap/