doc: linkify type[] syntax, support lowercase for primitives

PR-URL: https://github.com/nodejs/node/pull/11167


Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>