Add build hash in the dist JavaScript filename

[dunnock]

This will help to aviod collision with CDN where they can deliver old version of bundle if it's named the same also to be able to employ static hosting.

Can be easily done with HtmlWebpackPlugin:

  new HtmlWebpackPlugin({
    template: 'public/index.html',
    inject: false
  }),
  new ScriptExtHtmlWebpackPlugin({
    defaultAttribute: 'async'
  })

And at the bottom of public/index.html:

  <script async src="<%= htmlWebpackPlugin.files.js[0] %>"></script>