Add docs build workflow to CI
This PR adds a docs workflow to CI.
Maintenance will be performed on git.ligo.org, containers.ligo.org, and docs.ligo.org on Tuesday 2 July 2024 starting at approximately 9:30am PDT. It is expected to take around two hours and there will be several periods of downtime throughout the maintenance. Please address any comments, concerns, or questions to the helpdesk.
This PR adds a docs workflow to CI.