Use visitor pattern

[agentofuser]

It hadn't occurred to me that the visitor pattern could be used here, so I did the stack-based explicit recursion thing, but that only works it all the headings and content are top-level children of the root element. If they are already nested within, for instance, some arbitrary div, it doesn't work.

remark-sectionize does that much more elegantly.

[wooorm]

I just wrote about tree traversing in syntax-tree/unist#23!

[agentofuser]

That is very helpful, thank you!