integrate with rust doclinking (somehow...)

[vitiral]

I want to integrate with the new feature detailed here: rust-lang/rfcs#1990

I think the main point here is to export the full artifact objects to markdown. From there it should be FAIRLY easy to migrate.

I'm still not sure the best way to export to markdown. I've been playing with it my head for a while. Some options are:

• always have a "table of contents" with links to all artifact names
• aritfact names in partof and in text using the [[...]] notation would be linked correctly
• do each artifact in their own file? Reasons: possibly cleaner for "including" in source docs
• do all artifacts in a single file? Reasons: easier to "search" using normal browser. Might be hard to link against in source docs.