Documentation: Catch up documentation with Framework

[stichbury]

Description

I've recently made some improvements to the framework documentation to add some sphinx extensions with corresponding features. We should have the same on the Viz (and datasets) docs. Please can you factor in some time in the team to do the following:

• Add the video extension for youtube videos (e.g. if you want to include any of Juan Luis' videos). See the Framework PR for details.
• Add a favicon to the Viz docs + add "last updated" to the Viz docs: one PR here
• Update robots.txt to remove older versions from google indexing and also remove latest

[rashidakanchwala]

There seems to be two of the same PRs hence closing this because #1724