Improve CDN listing page(s)

[james-nash]

Is your feature request related to a problem? Please describe.
Copies of new gravity-ui-web releases get uploaded to our CDN here: https://static.buildit.digital/gravity-ui-web/

The index page you see at the URL is very basic, so it might be nice to spruce it up a bit. Specifically, things that would be nice are:

• More details for each release
  • Currently we just list out the version number. It would be good if we included direct links to the actual files in each Gravity release (e.g. gravity.css, gravity.js etc.), since that's what people using the CND will ultimately be after. This could be a little list of filenames (each of which is a link to the corresponding file) OR we could add an index page for each release with that file listing and then link to that. (The latter option might help the main index page from becoming excessively long)
  • A link to the corresponding NPM package version on npmjs.com
  • A link to that versions release notes on Github
• A page header
  • Something to give visitors some context. I.e. what is this page for?
• A page footer
  • Provide some links back to the main Buildit website and Gravity pattern library

Describe the solution you'd like

1. Make some lo-fi mockups to explore the above ideas. Pen & paper would do. Maybe a CodePen or two if you're feeling adventurous. Share on the #buildit-gravity Slack channel for feedback from the rest of the team
2. Update cdn-index.template and scripts/cdn_publish.sh as necessary. My hunch is that we may need replace or augement them with something a little more sophisticated. Using a bash script to string together bits of HTML is a bit clunky. Maybe a little Node.js script would be easier? Potentially it could even make use of some of the Nunjucks templates we have within gravity-ui-nunjucks?