doc: add bcoe as collaborator

PR-URL: https://github.com/nodejs/node/pull/21536


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Matheus Marchini <matheus@sthima.com>