Add nicohartmann@ as an owner.

Change-Id: I7c24b1ab575db857a15cff709f44c87c74106d80
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2593332Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72048}