add plug for SimpleBusyBox because a few play store reviews asked for busybox

doc/index.html

@@ -45,6 +45,9 @@ file.</p>
 is supported.  If you screw up your <tt>authorized_keys</tt> file, use
 the options menu (upper right) -> Reset Keys.</p>
 
+<p>Once you get setup, you may want BusyBox.  Check out
+<a href="https://play.google.com/store/apps/details?id=org.galexander.busybox">SimpleBusyBox</a>.</p>
+
 <h2>Settings</h2>
 
 <p>Generally speaking, you must re-start the SimpleSSHD service for any