[DOCS] Adds more info to whats new (#147294)

## Summary

This PR adds information on:

- The read-only Users and Roles views
- Email notifications in case assignments

docs/user/whats-new.asciidoc

@@ -79,10 +79,7 @@ image::images/highlights-maps-color-ramp.png[Map showing intense colors because
 
 
 [discrete]
-=== Machine Learning
-
-[discrete]
-==== Anomaly explanation
+=== More anomaly info in Machine Learning
 
 Additional information is now available on the anomaly table to help explain why something is
 anomalous and to show that the anomaly score has significantly changed from its initial value.
@@ -90,3 +87,19 @@ Each explanatory item has tooltips that help users better understand the anomaly
 
 [role="screenshot"]
 image::images/highlights-anomaly.png[Tooltip in anomaly table]
+
+[discrete]
+=== Read-only views in Security
+
+{kib} now has read-only versions of the *Users* and *Roles* management views.
+These views are for
+users with the newly introduced `read_security` cluster privilege in {es}.
+
+[discrete]
+=== Email notifications for case assignments
+
+Enhancing the case assignment capability, this release
+adds email notifications when a user is assigned a case.
+This draws users' attention to the assignment, and enables them to act more quickly on the assignment.
+Email notifications include the case title, status, severity,
+and tags, and a link to the case in {kib}.