[FAB-6911] Index change for peer services doc

Putting document in table of contents.
[ci-skip]

Change-Id: Iea5bd0a25266139a16f4465da3655f9ac4eb955b
Signed-off-by: joe-alewine <Joe.Alewine@ibm.com>

Author: joe-alewine

docs/source/index.rst

@@ -86,6 +86,7 @@ Business:
    kafka
    channels
    couchdb_as_state_database
+   peer_event_services
    readwrite
    gossip