Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: I15ad75e8e7c0dff63f495c18e688dabe692ee870
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..93337af
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,4 @@
+# Default code reviewers picked from top 3 or more developers.
+# Please update this list if you find better candidates.
+marcone@google.com
+dwkang@google.com