Data pipeline

[maxkfranz]

Build a data pipeline that generates data for all of the paper categories. The UI simply pulls in this data.

The build should...

• ... have fresh data every day.
• ... generate one or more JSON files that the UI can pull in statically.
• ... use the downloader, previously built.
• ... create data for each category that we support. See also #19.
• ... more TODO

[maxkfranz]

Ref: https://github.com/marketplace/actions/cloudflare-pages-github-action