res/res_pjsip_pubsub: Note that 'dialog' is also a valid event type for RLS

In addition to specifying lists of 'presence' and 'message-summary',
users can also create lists of type 'dialog'. These should be treated in
the same fashion as 'presence'.

Change-Id: I583bb69cd9f88b0b29bf09ddaddeac4e84189f6e

res/res_pjsip_pubsub.c

@@ -148,6 +148,9 @@
 							<enum name="presence"><para>
 								Device state and presence reporting.
 							</para></enum>
+							<enum name="dialog"><para>
+								This is identical to <replaceable>presence</replaceable>.
+							</para></enum>
 							<enum name="message-summary"><para>
 								Message-waiting indication (MWI) reporting.
 							</para></enum>