Add myself to OWNERS

Change-Id: I60fbbc1db1833422abcc81d2fff19d6dc1d9c198
diff --git a/OWNERS b/OWNERS
index 5c0d0bd..71095e5 100644
--- a/OWNERS
+++ b/OWNERS
@@ -3,3 +3,4 @@
 haining@google.com
 malchev@google.com
 schuffelen@google.com
+astrachan@google.com