Added searchbox to documentation.

This provides the entry point of the documentation search feature.

Change-Id: Iea2b707995c0e042829db509927384dcec7aaf43

Documentation/error-has-duplicates.txt

diff --git a/Documentation/error-has-duplicates.txt b/Documentation/error-has-duplicates.txt
index b5175c0..4eac779 100644
--- a/Documentation/error-has-duplicates.txt
+++ b/Documentation/error-has-duplicates.txt
@@ -22,3 +22,6 @@
 GERRIT
 ------
 Part of link:error-messages.html[Gerrit Error Messages]
+
+SEARCHBOX
+---------