Update index.html

Author: Maxw3llGM

index.html

@@ -36,6 +36,7 @@ <h4>Input Devices and Musical Interaction Laboratory (IDMIL) - <a href="//www.id
 
     <ul>
       <li><a href="tutorials">Tutorial on Sampling and Quantization</a></li>
+      <li><a href="delta-modulation">Tutorial on Delta Modulation</a></li>
       <li><a href="all-panels">all panels and sliders</a> (mainly for developers)</li> 
     </ul>