add ftang as owner

Change-Id: Ibbf0b2fd183d40445930c4197b92fd3b5bb2c40b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2158487Reviewed-by: Nebojša Ćirić <cira@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67379}

INTL_OWNERS

 cira@chromium.org
 mnita@google.com
 jshin@chromium.org
+ftang@chromium.org