Added extra parameter to npm start script to avoid webpack-dev-server…

… ipv6 problem

When running the project as is using `npm start` no page was served on http://localhost:8080/ on my machine.
This is due to webpack-dev-server is using IPV4 and newer laptops and browsers are using IPV6.
The issue is fixed here: webpack/webpack-dev-server#676

Adding `--host ::` will ensure the project runs and serves the page correctly on newer browsers.

js/start.md

@@ -70,7 +70,7 @@ Add the following to the `package.json` file:
     "webpack-dev-server": "^3.1.5"
   },
   "scripts": {
-    "start": "webpack && webpack-dev-server --mode development",
+    "start": "webpack && webpack-dev-server --mode development --host ::",
     "build": "webpack"
   }
 }