Add default code reviewers into OWNERS

Bug: 33166666
Test: gerrit uploader
Change-Id: Ieb502c0d3f9b421aca494ba8bbbe7003082a09e4
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..ccae854
--- /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.
+include platform/tools/tradefederation:/OWNERS