static after(elem, target) {
    const parent = target.parentNode;

    if (parent.lastChild === target) {
      parent.appendChild(elem);
    } else {
      parent.insertBefore(elem, target.nextSibling);
    }
  }
Inserts and element after another element.
@param {Element} elem the element to be inserted.
@param {Element} target the element to be inserted after.