Edit babel configuration in create-elm-app

elmapp.config.js

module.exports = {
  configureWebpack: (config, env) => {
    const rules = config.module.rules
    rules
      .map(r => {
        // find js rule
        if (r.test && r.test.toString().indexOf('js') > -1) {
          // find the rule with the actual babel config
          if (r.use) {
            r.use[0].options.plugins = r.use[0].options.plugins || []
            r.use[0].options.plugins.push('@babel/plugin-syntax-dynamic-import')
          }
        }
      })
    return config
  }
}