Add release highlights to 3.9

Change-Id: Ib2b691f1e8ebf3b420d8cdac1d77da598b9b21cb
diff --git a/pages/site/releases/README.md b/pages/site/releases/README.md
index dd65e3a..798c19a 100644
--- a/pages/site/releases/README.md
+++ b/pages/site/releases/README.md
@@ -50,6 +50,22 @@
 
 ## 3.9
 
+* Java 17
+
+* New stream events
+
+* New limits
+
+* New diff3 view
+
+* Attention-set improvements
+
+* Indexing improvements
+
+* Account deletion
+
+* User Suggested Edits
+
 [Release notes for Gerrit 3.9](/3.9.html)
 
 ## 3.8