Add example of extending Gerrit's top menu item

Add a "Browse Repositories" item in the "Projects" menu.

Change-Id: I67af5bca1a14288147b1bc43fb089ba0abe0d6b2
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloTopMenu.java b/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloTopMenu.java
index ae8acbb..d7a4bf0 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloTopMenu.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cookbook/HelloTopMenu.java
@@ -31,6 +31,8 @@
     menuItems.add(new MenuItem("Documentation", baseUrl));
     menuEntries = Lists.newArrayListWithCapacity(1);
     menuEntries.add(new MenuEntry("Cookbook", menuItems));
+    menuEntries.add(new MenuEntry("Projects", Lists.newArrayList(
+        new MenuItem("Browse Repositories", "https://gerrit.googlesource.com/"))));
   }
 
   @Override