code: function es(cb) {
    const env = process.env.NODE_ENV || 'development';
    rollup({
      input: './src/ssr-window.js',
      plugins: [buble()],
      format: 'es',
      name: 'ssrWindow',
      strict: true,
      sourcemap: env === 'development',
      banner,
    })
      .pipe(source('ssr-window.js', './src'))
      .pipe(buffer())
      .pipe(rename('ssr-window.esm.js'))
      .pipe(gulp.dest(`./${env === 'development' ? 'build' : 'dist'}/`))
      .on('end', () => {
        if (cb) cb();
      });
  }
docs: ES MODULE DIST