[DOCS] Add 8.13.4 release notes (#2226) (#2235)

(cherry picked from commit f44750f)

Author: jbaiera

docs/src/reference/asciidoc/appendix/release-notes/8.13.4.adoc

@@ -0,0 +1,5 @@
+[[eshadoop-8.13.4]]
+== Elasticsearch for Apache Hadoop version 8.13.4
+
+ES-Hadoop 8.13.4 is a version compatibility release, tested specifically against
+Elasticsearch 8.13.4.

docs/src/reference/asciidoc/appendix/release.adoc

@@ -9,6 +9,7 @@ This section summarizes the changes in each release.
 [[release-notes-8]]
 ===== 8.x
 
+* <<eshadoop-8.13.4>>
 * <<eshadoop-8.13.3>>
 * <<eshadoop-8.13.2>>
 * <<eshadoop-8.13.1>>
@@ -106,6 +107,7 @@ Elasticsearch 5.3.1.
 
 ////////////////////////
 
+include::release-notes/8.13.4.adoc[]
 include::release-notes/8.13.3.adoc[]
 include::release-notes/8.13.2.adoc[]
 include::release-notes/8.13.1.adoc[]