function addInertStyle(node) {
  if (node.querySelector('style#inert-style')) {
    return;
  }
  const style = document.createElement('style');
  style.setAttribute('id', 'inert-style');
  style.textContent = "\n"+
                      "[inert] {\n" +
                      "  pointer-events: none;\n" +
                      "  cursor: default;\n" +
                      "}\n" +
                      "\n" +
                      "[inert], [inert] * {\n" +
                      "  user-select: none;\n" +
                      "  -webkit-user-select: none;\n" +
                      "  -moz-user-select: none;\n" +
                      "  -ms-user-select: none;\n" +
                      "}\n";
  node.appendChild(style);
}
Adds a style element to the node containing the inert specific styles
@param {Node} node