scrapbox.PageMenu('NewButton').addItem({
  title: 'NewButton',
  image: 'https://i.gyazo.com/7057219f5b20ca8afd122945b72453d3.png',
  onClick: () => alert('Hello, Scrapbox!'),
});
scrapbox.PageMenu('NewButton').addItem({
  title: () => `${new Date()}`,
  image: 'https://img.icons8.com/ios/180/clock.png',
  onClick: () => alert('Hello, Scrapbox!'),
});