Add parent:foo search operator to the 2.16.5 release notes

Change-Id: I30eccb8d8b1d5f970c0c0fe8e8ea09abcc919aeb
diff --git a/pages/site/releases/2.16.md b/pages/site/releases/2.16.md
index 09a8fdd..b21325a 100644
--- a/pages/site/releases/2.16.md
+++ b/pages/site/releases/2.16.md
@@ -492,6 +492,12 @@
 
 ### 2.16.5
 
+#### New features
+
+Allow searching for projects by parent project name, using the 'parent:foo' search operator in the query string.
+See the [projects search operator documentation](https://gerrit-documentation.storage.googleapis.com/Documentation/2.16.5/user-search-projects.html#search-operators)
+for more details.
+
 #### Dependency Updates
 
 * [Issue 10024](https://bugs.chromium.org/p/gerrit/issues/detail?id=10024): Upgrade Jetty to 9.4.14.v20181114