Assign myself as webview doc OWNER

BUG=none

Review URL: https://codereview.chromium.org/309053003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274288 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/docs/OWNERS

 # For documentation.
-awatson@chromium.org
 mkearney@chromium.org
 mkwst@chromium.org
 scheib@chromium.org
 
+# For webview documentation.
+fsamuel@chromium.org
+
 # For server related things (Python, JavaScript, templates, etc).
 kalman@chromium.org