Add delay waveform image to GUI documentation

gui/list.html

 </script>
 <script type="text/x-red" data-help-name="AudioEffectDelay">
 	<h3>Summary</h3>
+	<div>
 	<p>Delay a signal.  Up to 8 separate delay taps can be used.</p>
+	<p align=center><img src="delay.png"><br><small>1 kHz burst, delayed 5.2 ms.</small></p>
+	</div>
 	<h3>Audio Connections</h3>
 	<table class=doc align=center cellpadding=3>
 		<tr class=top><th>Port</th><th>Purpose</th></tr>