Add # COMPONENT to OWNERS

See https://tinyurl.com/yxau5sc4 for context.

Bug: 977050
Change-Id: Ia350e71825604e5554f74e38f1223e49db2082b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808100
Commit-Queue: Eric Foo <efoo@chromium.org>
Auto-Submit: Eric Foo <efoo@chromium.org>
Reviewed-by: Max Morin <maxmorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698549}

third_party/pffft/OWNERS

 maxmorin@chromium.org
 olka@chromium.org
+
+# COMPONENT: Blink>WebRTC>Audio