doc: add MoonBall to collaborators

PR-URL: https://github.com/nodejs/node/pull/19109


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>