[DOCS] Adds machine learning 6.4.0 highlights (#32861)

Author: lcawl

docs/reference/release-notes/highlights-6.4.0.asciidoc

@@ -15,6 +15,22 @@ See also <<release-notes-6.4.0,{es} 6.4.0 release notes>>.
 * Korean analysis tools - A new plugin has been added which provides analysis tools for the Korean language. The new `nori` analyzer can be used to analyze Korean text "out of the box" and custom analyzers can use a tokenizer, part of speech token filter and a Hanja reading form token filter. For more information, see {plugins}/analysis-nori.html[Nori Plugin].
 * Add multiplexing token filter - This new token filter allows you to run tokens through multiple different tokenfilters and stack the results. For example, you can now easily index the original form of a token, its lowercase form and a stemmed form all at the same position, allowing you to search for stemmed and unstemmed tokens in the same field. For more information, see <<analysis-multiplexer-tokenfilter,Multiplexer token filter>>.
 
+[float]
+=== Machine learning
+
+* Improve your machine learning results with custom rules. If you want to fine 
+tune your machine learning results (for example, to skip anomalies related to 
+certain servers), you can now create custom rules in {kib} and by using {ml} APIs. 
+Custom rules instruct anomaly detectors to change their behavior based on 
+domain-specific knowledge that you provide. See 
+{stack-ov}/ml-configuring-detector-custom-rules.html[Customizing detectors with custom rules]
+* The {ml} analytics can now detect specific change points in a time series, 
+such as step changes, linear scaling, and time shifts (for example, related to 
+daylight savings). There is also a new probability model that can predict when 
+step changes might occur. As a result, the {ml} results are more robust and can 
+make more accurate predictions when these types of changes are present in your 
+data. 
+
 [float]
 === Mappings
 
@@ -41,3 +57,4 @@ changes ranges include https://github.com/elastic/elasticsearch/pulls?q=is%3Aclo
 
 Specifically we want to highlight the https://github.com/elastic/elasticsearch/pull/30414[added support for AWS session tokens] to both 
 the EC2 discovery plugin and the S3 repository plugins. This allows Elasticsearch to use AWS devices protected by multi factor authentication.
+