This is a GatsbyJS site, on top of Netlify CMS for now, and powered by YAML files.
Swing by src/data/links/ to see all the links, and if you'd like to add a new one just copy and paste one of the older ones and update it.
We're working on rewriting this whole thing to Statamic, and that rewrite does an import of the YAML mentioned above, then converts it with node convert.js. Check out the api/ directory for that, and the Statamic v3 Beta Documentation.
Things are a tad confusing at the moment, but swing by our issues or @philsturgeon on Twitter. We'll get it cleared up soon.