title: Webpack Dev Server Config - contentBase not working
body: <p>I'm trying to setup a webpack dev server but for a reason, I'm running into an error.</p>
  <blockquote>
  <p>[webpack-cli] Invalid options object. Dev Server has been initialized using an options object that does not match the API schema.
  options has an unknown property 'contentBase'. These properties are valid:
  object { allowedHosts?, bonjour?, client?, compress?, devMiddleware?, headers?, historyApiFallback?, host?, hot?, http2?, https?, ipc?, liveReload?, magicHtml?, onAfterSetupMiddleware?, onBeforeSetupMiddleware?, onListening?, open?, port?, proxy?, server?, setupExitSignals?, static?, watchFiles?, webSocketServer? }</p>
  </blockquote>
  <p>I did install all the needed packages globally and tried some other suggestions but I cannot get it to work.</p>
  <p>This is the config:</p>
  <pre><code>const path = require('path');
  
  module.exports = {
      entry: './app/Main.js',
      output: {
          publicPath: '/',
          path: path.resolve(__dirname, 'app'),
          filename: 'bundled.js',
      },
      mode: 'development',
      devtool: 'source-map',
      devServer: {
          port: 3000,
          contentBase: path.join(__dirname, 'app'),
          hot: true,
          historyApiFallback: { index: 'index.html' },
      },
      module: {
          rules: [
              {
                  test: /\.js$/,
                  exclude: /(node_modules)/,
                  use: {
                      loader: 'babel-loader',
                      options: {
                          presets: [
                              '@babel/preset-react',
                              ['@babel/preset-env', { targets: { node: '12' } }],
                          ],
                      },
                  },
              },
          ],
      },
  };
  </code></pre>
  <p>My files:<br />
  <a href="https://i.stack.imgur.com/8TEWC.png" rel="noreferrer">enter image description here</a></p>
  <p>Looking forward to ur answers! Thanks</p>