Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: Id7be5e0719dde085ac4c2ef978d84c4516014fbc
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..9512b05
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,3 @@
+# Default code reviewers picked from top 3 or more developers.
+# Please update this list if you find better candidates.
+allight@google.com