title: How to remove @charset in the CSS file when running npm?
body: <p>I'm using Laravel 5.7 and i'm applying AMP to our website. (<a href="https://amp.dev/" rel="nofollow noreferrer">https://amp.dev/</a>).</p>
  
  <p>I'm folowing these steps to convert HTML to AMP: <a href="https://amp.dev/documentation/guides-and-tutorials/start/converting/?format=websites" rel="nofollow noreferrer">https://amp.dev/documentation/guides-and-tutorials/start/converting/?format=websites</a></p>
  
  <p>One of the requirements is to replace external stylesheets to internal stylesheets (<a href="https://amp.dev/documentation/guides-and-tutorials/start/converting/resolving-errors?format=websites#replace-external-stylesheets" rel="nofollow noreferrer">https://amp.dev/documentation/guides-and-tutorials/start/converting/resolving-errors?format=websites#replace-external-stylesheets</a>). I've done this by doing the following code below:</p>
  
  <pre><code>&lt;style amp-custom&gt;
      {!! file_get_contents(public_path('css/app.css')) !!}
  &lt;/style&gt;
  </code></pre>
  
  <p>I'm using Sass and I'm using Laravel mix to compile my assets.</p>
  
  <p>This is my <code>webpack.mix.js</code></p>
  
  <pre><code>const mix = require('laravel-mix');
  
  mix.js('resources/js/app.js', 'public/js')
     .sass('resources/sass/app.scss', 'public/css')
     .sourceMaps()
     .version();
  </code></pre>
  
  <p>But upon doing this I've encountered an error in the AMP:</p>
  
  <pre><code>CSS syntax error in tag 'style amp-custom' - saw invalid at rule '@charset'.
  </code></pre>
  
  <p>To solve this problem, I must remove the <code>@charset "UTF-8";</code> in the compiled css <code>css/app.css</code>. And it seems that running <code>npm run dev</code>, its automatically adding <code>@charset "UTF-8";</code> at the top of the file. How do I remove this?</p>
  
  <p>I'm thinking that I have to add some code in the <code>webpack.mix.js</code> to remove that. But I don't have an idea how to do this.</p>