Here is some CSS that I’ve used to put a progress bar at the top of the screen:
<!-- Progress Bar -->
<pre><span><style>
#app-root div[opacity='1'] {
content: "";
color: transparent;
display: block;
height: 45px;
background-image: url("IMAGE_URL");
background-size: 260px 20px;
background-repeat: no-repeat;
background-position: 55% 45%;
}
Replace IMAGE_URL with a pointer to the image you want to use.
You may need to fiddle with it a bit for your specific use case.