Design new "stories showcase" page

[mradamcox]

We need a new page for the US Covid Atlas that summarizes the Atlas Histories portion of the work and has a showcase of a few stories (lots of flexibility in what goes into it, these are just general elements of it).

This page will fit within the main atlas website, not on stories.uscovidatlas.org.

[mradamcox]

Here's a general design for the page, which should be pretty easy to create by duplicating and modifying the home page of the site. @Makosak will be completing the content once the basic structure has been generated.