pkg/ser: added readme with not that ser packaging specs are removed

pkg/ser/README.md

@@ -0,0 +1,9 @@
+# Packaging SER Application #
+
+Specs for packaging SER were removed, not being maintained for very long time.
+
+See the specs for Kamailio packaging for up to date rules, they are located at:
+
+  * pkg/kamailio/
+
+For questions, email to [email protected] .