Wasm demos: add touch-action: none to all canvas

So that the Slider, Flickabke and such works on android/chrome

examples/plotter/index.html

@@ -19,6 +19,8 @@
             animation: spinner 1s ease infinite;
         }
         @keyframes spinner { to { transform: rotate(360deg); } }
+
+        canvas { touch-action: none; }
         /* beautify ignore:end */
     </style>
 </head>