Migrate API docs stuff to core repo somehow

[Trott]

It's important that people working on docs in the core repository are able to see what their changes will look like there. Right now, we run make docs and get a directory of web assets that we can view in a browser without even starting a web server--just use the file: URL--and we get exactly what will be rendered on nodejs.org.

This repository makes modifications. In discussion today at the WG meeting, we concluded that we can probably make it work in nodejs.org. Various approaches were discussed and I'm not going to try to summarize (because I hope others with more knowledge will) but we should figure an approach and go for it (while being prepared to stop and try again with another approach if we hit a blocker).