Function add

src/helpers/classList.js:115–120

(element, classString)

 *                           with ' ' as separator.
 */
export const add = (element, classString) =>
  trackClass(
    element.classList,
    element.nodeName.toLowerCase() == "html" ? htmlClassList : docBodyClassList,
    classString.split(" ")
  );

/**
 * Public inferface to remove classes from the document.body.