[Docs] 8.15.4 release notes (elastic#198565)

## Summary

Adding a section for 8.15.4 release notes.

---------

Co-authored-by: Florent Le Borgne <[email protected]>
Co-authored-by: Liam Thompson <[email protected]>
(cherry picked from commit bab2c2a)

# Conflicts:
#	docs/CHANGELOG.asciidoc

docs/CHANGELOG.asciidoc

@@ -10,6 +10,11 @@
 
 Review important information about the {kib} 8.x releases.
 
+<<<<<<< HEAD
+=======
+* <<release-notes-8.16.0>>
+* <<release-notes-8.15.4>>
+>>>>>>> bab2c2a497e ([Docs] 8.15.4 release notes (#198565))
 * <<release-notes-8.15.3>>
 * <<release-notes-8.15.2>>
 * <<release-notes-8.15.1>>
@@ -75,6 +80,34 @@ Review important information about the {kib} 8.x releases.
 --
 
 
+[[release-notes-8.15.4]]
+== {kib} 8.15.4
+
+The 8.15.4 release includes the following bug fixes.
+
+[float]
+[[fixes-v8.15.4]]
+=== Bug fixes
+Dashboards and visualizations::
+* Fixes incomplete string escaping and encoding in *TSVB* ({kibana-pull}196248[#196248]).
+* Adds scroll margin to panels ({kibana-pull}193430[#193430]).
+* Fixes an issue where label truncation in heat map legends was not working properly in *Lens* ({kibana-pull}195928[#195928]).
+Discover::
+* Fixes the width for saved object Type column ({kibana-pull}194388[#194388]).
+Elastic Observability solution::
+* Changes the slice outcome from bad to good whenever there is no data during the slice window ({kibana-pull}196942[#196942]).
+Elastic Search solution::
+* Fixes a bug with the {ref}/es-connectors-network-drive.html[Network Drive connector] where advanced configuration fields were not displayed for CSV file role mappings with `Drive Type: Linux` selected ({kibana-pull}195567[#195567]).
+Elastic Security solution::
+For the Elastic Security 8.15.4 release information, refer to {security-guide}/release-notes.html[_Elastic Security Solution Release Notes_].
+Kibana platform::
+* Fixes an issue causing the wrong date to show in the header of a report when generated from a relative date ({kibana-pull}197027[#197027]).
+* Fixes an issue with the export options for PNG/PDF reports in a dashboard ({kibana-pull}192530[#192530]).
+Machine Learning::
+* Fixes an issue preventing Anomaly swim lane panels from updating on query changes ({kibana-pull}195090[#195090]).
+Management::
+* Fixes the pagination of the source documents data grid in Transforms ({kibana-pull}196119[#196119]).
+
 [[release-notes-8.15.3]]
 == {kib} 8.15.3
 
@@ -100,7 +133,6 @@ Elastic Security solution::
 For the Elastic Security 8.15.3 release information, refer to {security-guide}/release-notes.html[_Elastic Security Solution Release Notes_].
 Kibana security::
 * Automatic Import no longer asks the LLM to map fields to reserved ECS fields ({kibana-pull}195168[#195168]).
-* Automatic Import no longer returns an "Invalid ECS field" message when the ECS mapping slightly differs from the expected format. For example `date_format` instead of `date_formats` ({kibana-pull}195167[#195167]).
 * Fixes an issue that was causing the Grok processor to return non-ECS compatible fields when processing structured or unstructured syslog samples in Automatic Import ({kibana-pull}194727[#194727]).
 * Fixes the integrationName when uploading a new version of an existing integration using a ZIP upload ({kibana-pull}194298[#194298]).
 * Fixes a bug that caused the Deploy step of Automatic Import to fail after a pipeline was edited and saved ({kibana-pull}194203[#194203]).