Use `position: absolute` for `<figcaption>`, not affecting the container's width. Also rewrite `<figure>` `<figcaption>` style.

The original method of adding an "external" icon is to append an `<img>` tag to `<a>` tags, but if the reader is viewing the content from a reader where the CSS style does not work, the image is displayed in an unwanted way.

The workaround is to remove the `<img>` tag and implement this feature with only CSS pseudo-element.

By context I mean necessary attributes, parents and brothers.

Now I can use bare ![]() instead of img shortcode to insert images with fancybox, lazyloading and caption.

Recommended format:

```markdown
![alt text](image_source "caption text")
```

- allow horizontal scroll when not having enough space on X axis
- maximun width for each cell