Add OWNERS file for samples/

R=mathias@chromium.org

BUG: v8:9247
Change-Id: I6dd7f2c80e2345038550051c634ce7338edade0f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1611680Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61494}

samples/OWNERS

+mathias@chromium.org
+yangguo@chromium.org