Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: Icc42712d9d04c73659b49539d1a2e89c2a12b53f
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..2136f15
--- /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.
+hhb@google.com
+pkanwar@google.com