All (properly formatted non-extension) websites will become RAINBOW!
it just works!™
If you want to add this to your site, just paste the HTML found below. Adjust the speed variable if the effect is to fast or slow.
<script>
var dg = 0
const speed = 10
setInterval(() => {
document.querySelector(':root').style.setProperty('filter', `hue-rotate(${dg}deg)`);
dg += speed
}, 100);
</script>