Determine how to integrate https://docs.voltocms.com/

[stevepiercy]

Determine how to integrate https://docs.voltocms.com/. Include in main docs or create a separate subdomain under plone.org?

@tiberiuichim will attempt to modify the Makefile in PR #1141 and on branch https://github.com/stevepiercy/documentation/blob/port-training-config/Makefile to use git submodules and pull content from that repo into this one.

[stevepiercy]

This was fixed in #1160 and we have a long-lived feature branch https://github.com/plone/volto/tree/plone6-docs in plone/volto#3001