Add # COMPONENT: Blink>Fonts>Emoji to OWNERS under third_party/emoji-segmenter

See https://docs.google.com/document/d/1tfRRv-kaGUiburkhRp1xCKnM8t6jqauacp8YIqMiZmk/preview for context.

Bug: 977050
Change-Id: I8b3ba1653908e10d1ee2c8698b35d16f4729d6bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808196
Auto-Submit: Eric Foo <efoo@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Eric Foo <efoo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698542}

third_party/emoji-segmenter/OWNERS

 behdad@chromium.org
 drott@chromium.org
 eae@chromium.org
+
+# COMPONENT: Blink>Fonts>Emoji