<!DOCTYPE html>
<head>
	<style>
    ::highlight(example) {
        background-color: yellow;
        color:green;
    }
</style>
</head>
<div id="target">
	<span id="highlight">highlight</span>
</div>

<script>
let highlight = document.getElementById('highlight');
let highlightRangeGroup = new HighlightRangeGroup(new StaticRange({startContainer: highlight.childNodes[0], startOffset: 0, endContainer: highlight.childNodes[0], endOffset: 4}));
CSS.highlights.set("example", highlightRangeGroup);
</script>