Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: Ice92f61c13d86faed20f02a8708dcccc39c1dc4a
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..0c1eae6
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,5 @@
+# Default code reviewers picked from top 3 or more developers.
+# Please update this list if you find better candidates.
+enh@google.com
+hhb@google.com
+senj@google.com