Add OWNERS file for //third_party/blink/web_tests/serial

Bug: 884928
Change-Id: I3692c3d9093d67572336c6d6270ff3370bc2683e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994274
Auto-Submit: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Ovidio de Jesús Ruiz-Henríquez <odejesush@chromium.org>
Reviewed-by: Ovidio de Jesús Ruiz-Henríquez <odejesush@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736971}

third_party/blink/web_tests/serial/OWNERS

+file://content/browser/serial/OWNERS
+
+# COMPONENT: Blink>Serial