[DOCS] Adds CCR to Stack Overview

Author: lcawl

docs/en/stack/index.asciidoc

@@ -32,6 +32,9 @@ include::{xes-repo-dir}/watcher/index.asciidoc[]
 :edit_url: https://github.com/elastic/stack-docs/edit/{branch}/docs/en/stack/ml/index.asciidoc
 include::ml/index.asciidoc[]
 
+:edit_url: https://github.com/elastic/elasticsearch/edit/{branch}/docs/reference/ccr/index.asciidoc
+include::{es-repo-dir}/ccr/index.asciidoc[]
+
 :edit_url:
 include::troubleshooting.asciidoc[]