Add 2.16.1 release notes/highlights to index. (#8419) (#8420)

Signed-off-by: Michael Montgomery <[email protected]>
(cherry picked from commit 5d17623)

Author: naemono

docs/release-notes/highlights.asciidoc

@@ -5,6 +5,7 @@
 --
 This section summarizes the most important changes in each release. For the full list, check <<eck-release-notes>>.
 
+* <<release-highlights-2.16.1>>
 * <<release-highlights-2.16.0>>
 * <<release-highlights-2.15.0>>
 * <<release-highlights-2.14.0>>
@@ -50,6 +51,7 @@ This section summarizes the most important changes in each release. For the full
 
 --
 
+include::highlights-2.16.1.asciidoc[]
 include::highlights-2.16.0.asciidoc[]
 include::highlights-2.15.0.asciidoc[]
 include::highlights-2.14.0.asciidoc[]