Image Caption in Jekyll

Interesting, I did something similar with my own static blog generator [0]. Instead of using an include I rewrote the CommonMark AST in such a way that an image directly followed by text (the caption) is rewritten.

    ![Alt text](cat.jpg)
    Photo of a cat.

is rendered as HTML as follows:

    <figure>
    <img alt="Alt text" src="cat.jpg" />
    <figcaption>
    Photo of a cat.
    </figcaption>
    </figure>

An advantage is that this allows for Markdown inside the caption itself. Not sure if your solution handles that.

[0] https://github.com/john-bokma/tumblelog

[1] http://johnbokma.com/blog/2019/09/16/rewriting-commonmark-no...