title: Unable to start a micro front-end app in single-SPA application
body: <p>I am facing error while trying to start sub-app in Single-SPA application. Basically, I am trying to develop a kind of util app (sub app in Single-SPA) which contains Sockjs, Stomp-client etc. I have removed node modules and package-lock.json and installed node modules again. When I try to start application I am facing below error.</p>
  <pre><code>Error:
  [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 'firewall'. These properties are valid:
     object { allowedHosts?, bonjour?, client?, compress?, devMiddleware?, headers?, historyApiFallback?, host?, hot?, http2?, https?, ipc?, liveReload?, onAfterSetupMiddleware?, onBeforeSetupMiddleware?, onListening?, open?, port?, proxy?, setupExitSignals?, static?, watchFiles?, webSocketServer? }
   - options.client has an unknown property 'host'. These properties are valid:
     object { logging?, overlay?, progress?, webSocketTransport?, webSocketURL? }
  </code></pre>
  <p>Command used for running the app : <code>npm start</code></p>
  <p><strong>package.json</strong></p>
  <pre class="lang-json prettyprint-override"><code>{
    &quot;name&quot;: &quot;@sudeep/livedoc&quot;,
    &quot;scripts&quot;: {
      &quot;start&quot;: &quot;webpack serve&quot;,
      &quot;start:standalone&quot;: &quot;webpack serve --env standalone&quot;,
      &quot;build&quot;: &quot;webpack --mode=production&quot;,
      &quot;analyze&quot;: &quot;webpack --mode=production --env analyze&quot;,
      &quot;lint&quot;: &quot;eslint src --ext js,ts,tsx&quot;,
      &quot;format&quot;: &quot;prettier --write .&quot;,
      &quot;check-format&quot;: &quot;prettier --check .&quot;,
      &quot;prepare&quot;: &quot;husky install&quot;,
      &quot;test&quot;: &quot;cross-env BABEL_ENV=test jest --passWithNoTests&quot;,
      &quot;watch-tests&quot;: &quot;cross-env BABEL_ENV=test jest --watch&quot;,
      &quot;coverage&quot;: &quot;cross-env BABEL_ENV=test jest --coverage&quot;
    },
    &quot;devDependencies&quot;: {
      &quot;@babel/core&quot;: &quot;^7.14.6&quot;,
      &quot;@babel/eslint-parser&quot;: &quot;^7.14.7&quot;,
      &quot;@babel/plugin-transform-runtime&quot;: &quot;^7.14.5&quot;,
      &quot;@babel/preset-env&quot;: &quot;^7.14.7&quot;,
      &quot;@babel/preset-typescript&quot;: &quot;^7.14.5&quot;,
      &quot;@babel/runtime&quot;: &quot;^7.14.6&quot;,
      &quot;babel-jest&quot;: &quot;^27.0.5&quot;,
      &quot;concurrently&quot;: &quot;^6.2.0&quot;,
      &quot;cross-env&quot;: &quot;^7.0.3&quot;,
      &quot;eslint&quot;: &quot;^7.29.0&quot;,
      &quot;eslint-config-prettier&quot;: &quot;^8.3.0&quot;,
      &quot;eslint-config-ts-important-stuff&quot;: &quot;^1.1.0&quot;,
      &quot;eslint-plugin-prettier&quot;: &quot;^3.4.0&quot;,
      &quot;husky&quot;: &quot;^6.0.0&quot;,
      &quot;identity-obj-proxy&quot;: &quot;^3.0.0&quot;,
      &quot;jest&quot;: &quot;^27.0.5&quot;,
      &quot;jest-cli&quot;: &quot;^27.0.5&quot;,
      &quot;prettier&quot;: &quot;^2.3.2&quot;,
      &quot;pretty-quick&quot;: &quot;^3.1.1&quot;,
      &quot;ts-config-single-spa&quot;: &quot;^2.0.1&quot;,
      &quot;typescript&quot;: &quot;^4.3.4&quot;,
      &quot;webpack&quot;: &quot;^5.40.0&quot;,
      &quot;webpack-cli&quot;: &quot;^4.7.2&quot;,
      &quot;webpack-config-single-spa&quot;: &quot;^4.0.0&quot;,
      &quot;webpack-config-single-spa-ts&quot;: &quot;^2.2.2&quot;,
      &quot;webpack-dev-server&quot;: &quot;^3.11.2&quot;,
      &quot;webpack-merge&quot;: &quot;^5.8.0&quot;
    },
    &quot;dependencies&quot;: {
      &quot;@types/jest&quot;: &quot;^26.0.23&quot;,
      &quot;@types/systemjs&quot;: &quot;^6.1.0&quot;,
      &quot;@types/webpack-env&quot;: &quot;^1.16.0&quot;,
      &quot;fast-json-patch&quot;: &quot;3.0.0-1&quot;,
      &quot;rxjs&quot;: &quot;6.6.0&quot;,
      &quot;stompjs&quot;: &quot;2.3.3&quot;,
      &quot;sockjs-client&quot;: &quot;1.5.0&quot;
    }
  }
  </code></pre>