feat(hints): pass shiftKey into onHintClicked

[twio142]

Support different actions on hint clicked depending on the shift key.

api.mapkey('yf', '#7Yank link url', () => {
  api.Hints.create('*[href]', (element, shiftKey) => {
    // without shift: copy link URL
    // with shift: copy markdown link
    const link = shiftKey ? `[${element.textContent}](${element.href})` : element.href;
    api.Clipboard.write(link);
  });
});