doc: add pronouns for tniessen to README

PR-URL: https://github.com/nodejs/node/pull/40412


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>