Adjust flex settings to push footer to bottom of short pages [BUG]

[djbpitt]

Expected behavior

Footer should cling to the bottom of all pages, including short pages. This is configurable with Flexbox; see https://philipwalton.github.io/solved-by-flexbox/demos/sticky-footer/.

Actual behavior

Footer lies below main content. When main content is short, footer does not reach bottom of page.

Reproduction steps

Open any short page, such as main page.