Adds APM release highlights to Installation Upgrade Guide (#375)

Author: lcawl

docs/en/install-upgrade/highlights.asciidoc

@@ -4,10 +4,27 @@
 Each release brings new features and product improvements. This section
 highlights notable new features and enhancements in {version}.
 
+//** <<apm-highlights,APM>>
 ** <<beats-highlights,Beats>>
 ** <<elasticsearch-highlights,{es}>>
 ** <<kibana-higlights,{kib}>>
 
+////
+[[apm-highlights]]
+=== APM highlights
+++++
+<titleabbrev>APM</titleabbrev>
+++++
+
+coming[7.3.0]
+
+This list summarizes the most important enhancements in APM.
+For the complete list, go to
+{apm-overview-ref-v}/apm-release-notes.html[APM release highlights].
+
+include::{apm-repo-dir}/apm-release-notes.asciidoc[tag=notable-v7-highlights]
+////
+
 [[beats-highlights]]
 === Beats highlights
 ++++