Attempt at tree shaking and code splitting combo 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.codesplit.js

const path = require('path');
const fs = require('fs')

const dir_js = path.resolve(__dirname, 'lib/es6_global/src/');
const dir_build = path.resolve(__dirname, 'dist');
const declaredom = 'node_modules/@ristostevcev/bs-declaredom/lib/es6_global/src/'

/**
NOTE: this currently doesn't work very well. The resulting code split ends up significantly larger than the
tree shaking alone, which shouldn't be the case. It should just have the declaredom stuff in a separate file so
that it can be versioned and cached by the browser, resulting in fast load times
**/

/*
```sh
Built at: 10/12/2019 12:58:05 PM
                                 Asset      Size  Chunks                   Chunk Names
                  declaredom.bundle.js  1.67 KiB       1  [emitted]        declaredom
              declaredom.bundle.js.map  8.17 KiB       1  [emitted] [dev]  declaredom
                       index.bundle.js  2.58 KiB       2  [emitted]        index
                   index.bundle.js.map  11.3 KiB       2  [emitted] [dev]  index
          vendors~declaredom.bundle.js   193 KiB       3  [emitted]        vendors~declaredom
      vendors~declaredom.bundle.js.map   799 KiB       3  [emitted] [dev]  vendors~declaredom
    vendors~declaredom~index.bundle.js   195 KiB       0  [emitted]        vendors~declaredom~index
vendors~declaredom~index.bundle.js.map  1.22 MiB       0  [emitted] [dev]  vendors~declaredom~index
```
*/

module.exports = {
    entry: {
      index: path.resolve(dir_js, 'Frontend.bs.js'),
      declaredom: [].concat(
        fs.readdirSync(declaredom)
          .filter(e => e.endsWith('.bs.js'))
          .map(filename => path.resolve(__dirname, declaredom, filename)),
        fs.readdirSync(declaredom + 'css/')
          .map(filename => path.resolve(__dirname, declaredom, 'css', filename)),
        fs.readdirSync(declaredom + 'html/')
          .map(filename => path.resolve(__dirname, declaredom, 'html', filename))
      )
    },
    output: {
      filename: '[name].bundle.js',
      chunkFilename: '[name].bundle.js',
      path: path.resolve(__dirname, 'dist'),
    },
    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
    },
    optimization: {
      splitChunks: {
        chunks: 'all',
      },
    },
    mode: 'production',
    // Create source maps for the bundle
    devtool: 'source-map',
};