Improve documentation, add Kubernetes section
Fixes
** xref:user-guide/command-mode.adoc[Command mode]
** xref:user-guide/testing.adoc[Testing]
** xref:user-guide/examples.adoc[Examples]
+** xref:user-guide/kubernetes.adoc[Kubernetes]
* xref:migration-guide/index.adoc[Migration guide]
** xref:migration-guide/2.0.0.adoc[Camel Quarkus 2.0.0 migration guide]
* xref:contributor-guide/index.adoc[Contributor guide]
