Adding OWNERS in /third_party/vulkan

Making sure there are at least 2 owners after I leave.
This CL was uploaded by git cl split.

R=penghuang@chromium.org

Change-Id: I16d9dc381699c884d6c335a16664b389fc82dc58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1674612
Auto-Submit: Antoine Labour <piman@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
Reviewed-by: Peng Huang <penghuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672065}

third_party/vulkan/OWNERS

+penghuang@chromium.org
 piman@chromium.org
 vmiura@chromium.org