This commit adds a version switch similar to the one on the user manual,
in the future it would be nice to refactor both of these into a more generic
code that works for both. Maybe develop this into a sphinx extension.
As part of this change I had to change how the blender hash is displayed.
Instead of the version hash in the top left it has been moved to the page footer.
This change will also be backported to 2.93 LTS, 2.93 LTS, and 3.0.
