[DOCS] Add 7.16.0 release notes (#1810)

Author: jrodewig

docs/src/reference/asciidoc/appendix/release-notes/7.16.0.adoc

@@ -0,0 +1,14 @@
+[[eshadoop-7.16.0]]
+== Elasticsearch for Apache Hadoop version 7.16.0
+
+[[new-7.16.0]]
+=== New Features
+Core::
+* Setting X-Opaque-ID header for all reads and writes for MapReduce and Spark
+https://github.com/elastic/elasticsearch-hadoop/pull/1770[#1770]
+
+[[bugs-7.16.0]]
+=== Bug Fixes
+Rest::
+* Closing RestRepository to avoid a connection leak
+https://github.com/elastic/elasticsearch-hadoop/pull/1781[#1781]

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

@@ -9,6 +9,7 @@ This section summarizes the changes in each release.
 [[release-notes-7]]
 ===== 7.x
 
+* <<eshadoop-7.16.0>>
 * <<eshadoop-7.15.2>>
 * <<eshadoop-7.15.1>>
 * <<eshadoop-7.15.0>>
@@ -108,6 +109,7 @@ http://github.com/elastic/elasticsearch-hadoop/issues/XXX[#XXX]
 
 ////////////////////////
 
+include::release-notes/7.16.0.adoc[]
 include::release-notes/7.15.2.adoc[]
 include::release-notes/7.15.1.adoc[]
 include::release-notes/7.15.0.adoc[]