Add release notes for 8.9.0 (#7861)

Author: flobernd

docs/release-notes/release-notes-8.9.0.asciidoc

@@ -0,0 +1,15 @@
+[[release-notes-8.9.0]]
+== Release notes v8.9.0
+
+[discrete]
+=== Bug fixes
+
+- https://github.com/elastic/elasticsearch-net/pull/7839[#7839] Use `Stringified<boolean>` for `preserve_original` and `indexing_complete` (issue: https://github.com/elastic/elasticsearch-net/issues/7755[#7755])
+- https://github.com/elastic/elasticsearch-net/pull/7840[#7840] Update `Elastic.*` dependencies (issue: https://github.com/elastic/elasticsearch-net/issues/7823[#7823])
+- https://github.com/elastic/elasticsearch-net/pull/7841[#7841] Fix typing of `BulkUpdateOperation.RetryOnConflict` (issue: https://github.com/elastic/elasticsearch-net/issues/7838[#7838])
+- https://github.com/elastic/elasticsearch-net/pull/7854[#7854] Fix custom floating-point JSON converters (issue: https://github.com/elastic/elasticsearch-net/issues/7757[#7757])
+
+[discrete]
+=== Enhancements
+
+- https://github.com/elastic/elasticsearch-net/pull/7836[#7836] Regenerate client using 8.9 specification

docs/release-notes/release-notes.asciidoc

@@ -3,6 +3,11 @@
 
 * <<breaking-changes-policy,Breaking changes policy>>
 
+[discrete]
+== Version 8.9
+
+* <<release-notes-8.9.0,Release notes v8.9.0>>
+
 [discrete]
 == Version 8.1
 
@@ -27,6 +32,7 @@
 * <<release-notes-8.0.0,Release notes v8.0.0>>
 
 include::breaking-change-policy.asciidoc[]
+include::release-notes-8.9.0.asciidoc[]
 include::release-notes-8.1.3.asciidoc[]
 include::release-notes-8.1.2.asciidoc[]
 include::release-notes-8.1.1.asciidoc[]