Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: Ib51cad306da1f9b35b39f7ba55fd1060f8e9c89a
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..563e6ae
--- /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.
+spaik@google.com
+yizheng@google.com