src/language-html/utils.js/isVueSfcBindingsAttribute
function isVueSfcBindingsAttribute(attribute, options) {
  const element = attribute.parent;
  if (!isVueSfcBlock(element, options)) {
    return false;
  }
  const tagName = element.fullName;
  const attributeName = attribute.fullName;

  return (
    // https://github.com/vuejs/rfcs/blob/sfc-improvements/active-rfcs/0000-sfc-script-setup.md
    (tagName === "script" && attributeName === "setup") ||
    // https://github.com/vuejs/rfcs/blob/sfc-improvements/active-rfcs/0000-sfc-style-variables.md
    (tagName === "style" && attributeName === "vars")
  );
}