Tree shaking only for bs-declaredom

Frontend.ml

let _ = Js.log "hello world!"

let x =
  let open RistostevcevBsDeclaredom.Html in
  div [|text "foobar"|]

let _ =
  if Js.Option.isSome HotModuleReload.module_hot then
    let _ = HotModuleReload.on_accept @@ fun () -> Js.log "accept: reloading..."
    and _ = HotModuleReload.on_dispose @@ fun () -> Js.log "dispose: reloading..."
    in ()

webpack.conf.treeshake.js

const path = require('path');

const dir_js = path.resolve(__dirname, 'lib/es6_global/src/');
const dir_build = path.resolve(__dirname, 'dist');

/**
This tree shakes reasonably well, but it would be nice to get code-splitting working with bs-declaredom so
that the browser can cache the declaredom stuff:

```sh
Built at: 10/12/2019 12:55:49 PM
                Asset      Size  Chunks                   Chunk Names
    bundle.webpack.js  47.2 KiB       0  [emitted]        main
bundle.webpack.js.map   800 KiB       0  [emitted] [dev]  main
```
**/


module.exports = {
    entry: path.resolve(dir_js, 'Frontend.bs.js'),
    output: {
        path: dir_build,
        filename: 'bundle.webpack.js'
    },
    devServer: {
        contentBase: dir_build,
    },
    module: {
      rules: [
        {
          sideEffects: false,
          test: /\.m?js$/,
          exclude: /(node_modules|bower_components)/,
          use: {
            loader: 'babel-loader',
            options: {
              presets: ['@babel/preset-env'],
              plugins: ['@babel/plugin-proposal-object-rest-spread']
            }
          }
        }
      ]
    },
    stats: {
        // Nice colored output
        colors: true
    },
    mode: 'production',
    // Create source maps for the bundle
    devtool: 'source-map',
};