Add carrier messaging engineers as owners of the mms code

Add the invididual engineers responsible for MmsService as owners
of the code.

Test: not applicable
Change-Id: Ia8e99d40a54b6f3c75cb48661f3be7ec79bda396
diff --git a/OWNERS b/OWNERS
index e2a657c..cc5e6a3 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,3 +1,7 @@
 amitmahajan@google.com
 rgreenwalt@google.com
-sanketpadawe@google.com
+tomtaylor@google.com
+afurtado@google.com
+jianxiangp@google.com
+stephshi@google.com
+bellavicevh@google.com