Single JSON collection for contact list

## Use Case

It might be preferable to store contact list as a single JSON collection, rather than have individual markdown files. Would likely require some refactoring to `onCreateNode` and maybe use `gatsby-transformer-json`

Could be more readable, could interop better with backend, or maybe not. Should look into whether there are benefits to establishing this pattern. In what context does anyone actually read this list, and does this make edits/PRs easier or harder?