To load up CSS files using JavaScript, we create an element with createElement.
For instance, we write
const link = document.createElement("link");
link.href = src;
link.rel = "stylesheet";
document.head.append(link);
to call createElement to create a link element.
And then we set its href and rel attributes by setting the properties with the same name.
Then we call document.head.append to append the link element as the last child of the head element.
