title: Laravel Mix 'watch' not compiling when webpack.mix.js updated
body: <p>When I run <code>npm run watch</code> and update my source <code>.js</code> and <code>.scss</code> assets, the compilation is run automatically as expected. When I update the <code>webpack.mix.js</code> file, the changes are NOT compiled automatically.</p>
  <p>Is this something that v6 doesn't support? Because v5 did work as expected.</p>
  <p>The config:</p>
  <pre class="lang-js prettyprint-override"><code>const mix = require('laravel-mix')
  
  mix.js('resources/js/app.js', 'public/js')
    .sass('resources/css/app.scss', 'public/css')
    .version()
  </code></pre>
  <p><code>package.json</code>:</p>
  <pre><code>{
    ...
  
    &quot;scripts&quot;: {
      &quot;development&quot;: &quot;mix&quot;,
      &quot;watch&quot;: &quot;mix watch&quot;,
      &quot;watch-poll&quot;: &quot;mix watch -- --watch-options-poll=1000&quot;,
      &quot;hot&quot;: &quot;mix watch --hot&quot;,
      &quot;production&quot;: &quot;mix --production&quot;
    }
  
    ...
  }
  </code></pre>