Added searchbox to documentation.

This provides the entry point of the documentation search feature.

Change-Id: Iea2b707995c0e042829db509927384dcec7aaf43
diff --git a/Documentation/cmd-show-caches.txt b/Documentation/cmd-show-caches.txt
index d426508..8c64b05 100644
--- a/Documentation/cmd-show-caches.txt
+++ b/Documentation/cmd-show-caches.txt
@@ -83,3 +83,6 @@
 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]
+
+SEARCHBOX
+---------