I am putting a spinning progress image in the center of the react root div as the loading progress indicator.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Full Screen Centered Spinning</title>
<style>
.loading{
display: flex;
flex-direction: row;
align-content: center;
justify-content: center;
min-height: 100vh; /* inner div to 100% screen height */
}
</style>
</head>
<body>
<div id="root">
<div class="loading">
<img alt="loading" src="images/spinner.svg" />
</div>
</div>
</body>
</html>
