title: add animation to fill progress bar
body: <p>How can i update it to fill progress bar with animation?</p>
  
  <p><a href="https://jsfiddle.net/dfkLexuv/2/" rel="nofollow noreferrer">https://jsfiddle.net/dfkLexuv/2/</a></p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.progress-bar-outer {
    width: 300px;
    height: 40px;
    flex: auto;
    display: flex;
    flex-direction: row;
    border-radius: 0.5em;
    overflow: hidden;
    background-color: gray;
  }
  
  .progress-bar-inner {
    /* You can change the `width` to change the amount of progress. */
    width: 75%;
    height: 100%;
    background-color: red;
  }
  
  .progress-bar-inner2 {
    /* You can change the `width` to change the amount of progress. */
    width: 50%;
    height: 100%;
    background-color: green;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="progress-bar-outer"&gt;
    &lt;div class="progress-bar-inner"&gt;
    &lt;/div&gt;
    &lt;div class="progress-bar-inner2"&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>