tools: produce JSON documentation using unified/remark/rehype

PR-URL: https://github.com/nodejs/node/pull/21697


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>