Don't allow images in Images example to be native draggable b/c it gets in the way of experimenting with UI

Author: lukemelia

addon/helpers/dynamic-image.js

@@ -30,6 +30,7 @@ export default function dynamicImage([imageSrc], hash) {
       img.setAttribute('class', className);
     }
     img.src = imageSrc;
+    img.draggable = false;
     return img;
   }
 }