Add zeromq.adoc to index files

* Fix Sonar smells for new ZeroMQ components
* Upgrade to Spring Data `2020.0.0-M2`

src/reference/asciidoc/index-single.adoc

@@ -87,6 +87,8 @@ include::./xml.adoc[]
 
 include::./xmpp.adoc[]
 
+include::./zeromq.adoc[]
+
 include::./zookeeper.adoc[]
 
 [[spring-integration-appendices]]

src/reference/asciidoc/index.adoc

@@ -53,6 +53,7 @@ This documentation is also available as single searchable link:index-single.html
 <<./ws.adoc#ws,Web Services Support>> ::
 <<./xml.adoc#xml,XML Support - Dealing with XML Payloads>> ::
 <<./xmpp.adoc#xmpp,XMPP Support>> ::
+<<./zeromq.adoc#zeromq,ZeroMQ Support>> ::
 <<./zookeeper.adoc#zookeeper,Zookeeper Support>> ::
 
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