Update Docs Importer

New node-based docs importer, to yank in JSDoc-formatted docs.

Also abstracted out the repo cloner for use in other scripts (planning to re-write `import_examples` to use it soon).

The one thing it won't do right now is extract breadboard images, but I think those should just be in the site, instead of in-repo and pulled into the site. Can look at adding that back if we want it.