CMS: Add the ability to add a site footer block to the _page-config

[Lallo Vigil]

I created a couple of sites that had site footers, but I'm only able to add them on the initial page:
https://colfaprod.utsa.edu/urbino/index.html
https://colfaprod.utsa.edu/mexico-center/index.html

[John David Garza]

added in both Walle and walledev