Revisit separated footer in contained cards

Our PWA Stats cards have a footer section that's separate from the rest of the card:

Which @AriannaChau accounted for in her designs for contained cards, seen here: #1282

But because those variations represent a significant layout change that would not be used by cloudfour.com proper, I decided to delay on implementing that portion for #1287.

So this issue is a placeholder that represents revisiting that PWA Stats design element at a later date. Possible outcomes may be:

- Implementing the footer as designed in #1282
- Re-thinking the design now that we have a fresh set of patterns to work with
- Punting this design element to PWA Stats entirely

Review the PWA Stats card footer shown in the issue and compare it with the contained-card designs in #1282 and the deferred work in #1287. First establish which outcome is wanted—implement the design, rethink it, or leave it to PWA Stats—then document the selected design and its completion criteria.

Written by the indexing model from the issue text.