Make Richard an OWNER of Web Notifications-related code

Change-Id: I6a3f622284c720130a91ee508bffd0d44d08848a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583707
Commit-Queue: Peter Beverloo <peter@chromium.org>
Commit-Queue: Richard Knoll <knollr@chromium.org>
Auto-Submit: Peter Beverloo <peter@chromium.org>
Reviewed-by: Richard Knoll <knollr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654430}

chrome/browser/notifications/OWNERS

 dewittj@chromium.org
 dimich@chromium.org
+knollr@chromium.org
 mukai@chromium.org
 peter@chromium.org
 stevenjb@chromium.org

content/browser/notifications/OWNERS

@@ -4,6 +4,7 @@
 # //content/renderer/notifications/
 # //content/test/mock_platform_notification_service.*
 
+knollr@chromium.org
 mkwst@chromium.org
 peter@chromium.org
 

third_party/blink/renderer/modules/notifications/OWNERS

+knollr@chromium.org
 peter@chromium.org
 
 # TEAM: platform-capabilities@chromium.org