"Loading" animation before loading page

add this line in as shown above
<div class='preloader-overlay' id='preloader__html'>
<aside class='loader'>
  <div class='loader-center'>
    <div class='chars'>
      <span class='char brace'>{</span>
      <span class='dots'>
        <span class='char dot _dot-1'>.</span>
        <span class='char dot _dot-2'>.</span>
        <span class='char dot _dot-3'>.</span>
      </span>
      <span class='char brace'>}</span>
    </div>
    <h6 style='letter-spacing:4px;'>Loading..</h6>
  </div>
</aside>
</div>