Update README.md (#175)

remove comma in demo

README.md

         font-size: 16px;
       }
     `}
-    onSizeUpdated={({size => console.log(size.height)})},
+    onSizeUpdated={({size => console.log(size.height)})}
     files={[{
         href: 'cssfileaddress',
         type: 'text/css',