Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: I266005b83789c2dadcbfb71b91f353364dc860ea
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..7529cb9
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/system/core:/janitors/OWNERS