Add COMPONENT: UI>Accessibility

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

Bug: 977050
Change-Id: If1168a9566a042902410d902057a09faafc1bc8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808310
Auto-Submit: Eric Foo <efoo@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698523}

components/page_image_annotation/OWNERS

 amoylan@chromium.org
 dmazzoni@chromium.org
 martis@chromium.org
+
+# COMPONENT: UI>Accessibility