Revert "Remove the Elasticsearch changelog"

This reverts commit fd1ac3b.

Author: javanna

conf.yaml

@@ -115,7 +115,10 @@ contents:
                 repo:   elasticsearch
                 path:   docs/Versions.asciidoc
                 exclude_branches:   [ 2.4, 2.3, 2.2, 2.1, 2.0, 1.7, 1.6, 1.5, 1.4, 1.3, 0.90 ]
-
+              -
+                repo:   elasticsearch
+                path:   docs/CHANGELOG.asciidoc
+                exclude_branches:   [ 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0, 2.4, 2.3, 2.2, 2.1, 2.0, 1.7, 1.6, 1.5, 1.4, 1.3, 0.90 ]
               -
                 repo:   x-pack-elasticsearch
                 prefix: elasticsearch-extra/x-pack-elasticsearch