Mention plugin-manager in 3.0 summary

Change-Id: Ibd73736e12941e9fe3741984d5542d68d05849b9
diff --git a/pages/site/releases/README.md b/pages/site/releases/README.md
index 3526b11..5637906 100644
--- a/pages/site/releases/README.md
+++ b/pages/site/releases/README.md
@@ -29,7 +29,7 @@
 
 * Support for signed push with GPG subkeys.
 
-* New core plugins: `delete-project`, `gitiles` and `webhooks`.
+* New core plugins: `delete-project`, `gitiles`, `plugin-manager` and `webhooks`.
 
 [Release notes for Gerrit 3.0](/3.0.md)