Add "# COMPONENT" to libyuv OWNERS file

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

Bug: 977050
Change-Id: I5b4f86267980bc97760aa23e1f28cbed890d8a9d
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/1846507Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>

OWNERS

@@ -6,3 +6,5 @@ per-file .gitignore=*
 per-file AUTHORS=*
 per-file DEPS=*
 per-file PRESUBMIT.py=phoglund@chromium.org
+
+# COMPONENT: Internals>Images>Codecs