<!-- section MASTHEAD -->
<seciton class="section seciton-masthead" data-background-color="var(--color-light-1)">
  ...
  <!-- js-transition-img and js-transition-img__transformed-el blocks are required for the image transition -->
  <div class="js-transition-img">
    <div class="js-transition-img__transformed-el">
      <div class="lazy-bg" data-src="img/assets/projects/project-4.jpg"></div>
    </div>
  </div>
  ...
  <!-- the rest markup is not important for the transition -->
</seciton>
<!-- - section MASTHEAD -->