This makes it possible for the footer to be reused in other places,
e.g. when templating blog posts (which do not go through
//web/tvl/template (yet)).
Change-Id: Ia8ab0e1c6db4f76b4de49239e11a4474038f60ae
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3773
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
