Function if

packages/dev/docs/src/Layout.js:459–461

(pageCategories.has(category))

  let categories = [];
  for (let category of CATEGORY_ORDER) {
    if (pageCategories.has(category)) {
      categories.push(category);
    } else if (category === '...') {
      for (let category of [...pageCategories].sort()) {
        if (!CATEGORY_ORDER.includes(category)) {
          categories.push(category);