doc: add Sam Roberts to TSC

Voted on async in the TSC repo.
This adds him to the TSC list in the README.

Fixes: https://github.com/nodejs/TSC/issues/687

PR-URL: https://github.com/nodejs/node/pull/27606


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>