doc: add thealphanerd to collaborators

PR-URL: https://github.com/nodejs/node/pull/3723


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>