Add fantasai to contributors.json
<rdar://problem/112296224>
Pull request: https://github.com/WebKit/WebKit/pull/15855
Committed 266077@main (bbbec87465c4): <https://commits.webkit.org/266077@main> Reviewed commits have been landed. Closing PR #15855 and removing active labels.
Committed 269110@main (c56a69161929): <https://commits.webkit.org/269110@main> Reviewed commits have been landed. Closing PR #18861 and removing active labels.