Migrate to gitlab pages

At the moment, the documentation is still being built on Alioth.

This needs to be migrated to Gitlab pages and then we need to redirect https://video.debconf.org to it.

added enhancement label

Once that is done, I have to remember to change the URLs to the doc from anonscm to salsa.

mentioned in merge request !3 (merged)

closed via commit af5837f6

closed via merge request !3 (merged)