Putting file back in side nav after 2 years MIA (hazelcast#1093)

This seemed the logical place to me.

It was originally under Architecture in the Reference section; then the other three files were moved here (the ones under Partition Groups and Networking), but this file was lost.

docs/modules/ROOT/nav.adoc

@@ -62,6 +62,7 @@ include::maintain-cluster:partial$nav.adoc[]
 ** xref:clusters:creating-clusters.adoc[Grouping Clusters]
 ** xref:clusters:partition-group-configuration.adoc[Grouping Partitions]
 ** xref:clusters:network-configuration.adoc[Networking]
+* xref:configuration:jet-configuration.adoc[]
 include::cluster-performance:partial$nav.adoc[]
 include::secure-cluster:partial$nav.adoc[]
 include::fault-tolerance:partial$nav.adoc[]