onAction callback for customButtons does not trigger "design:updated" event

[AlexPo91]

When using customButtons, content updated via the onAction callback updates visually but does not trigger the design:updated event. This prevents the builder from recognizing changes automatically, so a workaround (like adding an empty character) is currently needed to save updates.

customButtons: [
  {
    name: 'my_button',
    text: 'Gifs',
    icon: 'image',
    onSetup: () => {},
    onAction: (data, callback) => {
      handleOpenGiphyModal({ data, callback });
    },
  },
];



const handleUpdate = (url) => {
  callback(
    `${data.text}
      <div>
        <img
          src="${url}"
          width="300"
          height="300"
        />
      </div>`
  );
};

Expected Behavior:
Whenever content is updated through a custom button’s onAction callback, the design:updated event should be emitted so the builder automatically recognizes and saves changes.