Update index.html

Author: SueSmith

index.html

@@ -16,7 +16,7 @@
         <h1>I'm a website!</h1>
     </header>
         <div class="img-container">
-            <img class="illustration" src="cdn.svg" alt="CDN" />
+            <img class="illustration" src="cdn-icon.png" alt="CDN" />
         </div>
         <div class="instructions">
             <p>Oh hi! This is a <a href="https://github.com/glitchdotcom/glitchdotcom.github.io">website</a> you can use for demos.</p>