title: Webpack dev server 4.0.0 option `open` doens't work
body: <p>This is my <code>webpack.config.js</code>. With this setting the <code>liveReload</code> works(since by defualt it's <code>true</code>) while <code>open: true</code> didn't. When I run <code>./node_modules/.bin/webpack serve</code>, the browser doesn't opened automatically for me.</p>
  <pre><code>const path = require('path')
  const HtmlWebpackPlugin = require('html-webpack-plugin')
  
  
  module.exports = {
      mode: &quot;development&quot;,
      entry: &quot;./src/index.js&quot;,
      output: {
          filename: &quot;bundle.js&quot;,
          path: path.join(__dirname, 'dist'),
      },
      module: {
          rules: [
              {
                  test: /\.m?js$/,
                  exclude: /(node_modules)/,
                  use: {
                      loader: &quot;babel-loader&quot;,
                  },
              }
          ]
      },
      devServer: {
          static: {
              directory: path.join(__dirname, 'dist'),
          },
          open: {
              app: {
                  name: &quot;edge&quot;,
              }
          },
          port: 3003,
      },
      plugins: [
          new HtmlWebpackPlugin({
              template: './src/index.html',
              filename: 'index.html',
              inject: 'head',
              scriptLoading: 'defer'
          })
      ]
  }
  </code></pre>
  <p>here is the console message:</p>
  <pre><code>&gt; official-docs@1.0.0 server
  &gt; ./node_modules/.bin/webpack serve
  
  (node:97874) [DEP_WEBPACK_DEV_SERVER_CONSTRUCTOR] DeprecationWarning: Using 'compiler' as the first argument is deprecated. Please use 'options' as the first argument and 'compiler' as the second argument.
  (Use `node --trace-deprecation ...` to show where the warning was created)
  (node:97874) [DEP_WEBPACK_DEV_SERVER_LISTEN] DeprecationWarning: 'listen' is deprecated. Please use async 'start' or 'startCallback' methods.
  &lt;i&gt; [webpack-dev-server] Project is running at:
  &lt;i&gt; [webpack-dev-server] Loopback: http://localhost:3000/
  &lt;i&gt; [webpack-dev-server] On Your Network (IPv4): http://MY_IP:3000/
  &lt;i&gt; [webpack-dev-server] On Your Network (IPv6): http://[MY_IP2]:3000/
  &lt;i&gt; [webpack-dev-server] Content not from webpack is served from 'MY_PATH/babel-practice/official-docs/dist' directory
  asset bundle.js 1 MiB [emitted] (name: main)
  asset index.html 266 bytes [emitted]
  runtime modules 27 KiB 13 modules
  modules by path ./node_modules/core-js/ 252 KiB
    modules by path ./node_modules/core-js/internals/*.js 122 KiB 145 modules
    modules by path ./node_modules/core-js/modules/*.js 129 KiB 64 modules
  modules by path ./node_modules/webpack-dev-server/client/ 50.7 KiB 12 modules
  modules by path ./node_modules/webpack/hot/*.js 4.3 KiB 4 modules
  modules by path ./node_modules/html-entities/lib/*.js 81.3 KiB 4 modules
  modules by path ./node_modules/url/ 37.4 KiB 3 modules
  modules by path ./node_modules/querystring/*.js 4.51 KiB 3 modules
  ./src/index.js 3.1 KiB [built] [code generated]
  ./node_modules/jquery/dist/jquery.js 282 KiB [built] [code generated]
  ./node_modules/ansi-html/index.js 4.16 KiB [built] [code generated]
  ./node_modules/events/events.js 14.5 KiB [built] [code generated]
  webpack 5.48.0 compiled successfully in 974 ms
  </code></pre>