[root] Add global approvers

The global approvers should be able to approve changes everywhere in the
source tree to facilitate large-scale changes.

Change-Id: I4b2dea43014405047d2fd6670225d2f41031a236
diff --git a/OWNERS b/OWNERS
index 21d4a45..3c1c10d 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,3 +1,22 @@
+# Global approvers
+#
+# Please keep in sync with //OWNERS
+abarth@google.com
+abdulla@google.com
+cramertj@google.com
+ianloic@google.com
+jamesr@google.com
+jeffbrown@google.com
+jeremymanson@google.com
+kulakowski@google.com
+mcgrathr@google.com
+phosek@google.com
+pylaligand@google.com
+qsr@google.com
+raggi@google.com
+thatguy@google.com
+
+# //topaz OWNERS
 anwilson@google.com
 chaselatta@google.com
 jasoncampbell@google.com