Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: I587e9dca1359d68b5cc9058068838b3ec1f30e0b
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..671a4c2
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,2 @@
+shanyu@google.com
+dkrahn@google.com