title: MIME type error while using ES6 export/import
body: <p>How to get rid of "forbidden MIME type („text/html”)" error while using ES6 export/import?<br>My html:<br> 
  <code>&lt;script src="app.js" type="module"&gt;&lt;/script&gt;
  </code>
  app.js:</p>
  
  <pre><code>import {about} from "./templates/about"
  let contentContainer = document.getElementById('contentContainer');
  const routes = {
      "/" : about,
  }
  
  window.onpopstate = () =&gt;{
      contentContainer.innerHTML = routes[window.location.pathname];
  }
  console.log("script")
  </code></pre>
  
  <p>about.js:</p>
  
  <pre><code>export const about =`
  &lt;section class="about-us"&gt;
              &lt;div class="about-us-img"&gt;
                  &lt;div class="img-shader"&gt;
                      &lt;h1 class="about-title"&gt;ABOUT US&lt;/h1&gt;
                      &lt;article class="about-description"&gt;
                          &lt;p&gt;Our company specializes in high quality wooden products.&lt;/p&gt;
                          &lt;p&gt;We care about natural environment so we plant two trees for each one we cut down to make the product.&lt;/p&gt;
                      &lt;/article&gt;
                      &lt;button id="shop-link"&gt;shop now&lt;/button&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          &lt;/section&gt;
  `
  </code></pre>
  
  <p>Also i am using Firefox 73, liveserver extension to VSCode and this is client-side application.
  I've tried adding text/javascript type to script tag but this didn't help. </p>