Fix caption alignment with centered images

[stefaniebutland]

See image & caption at bottom of blog post: https://openscapes.org/blog/2024-07-18-openscapes-update/

Captions are left-aligned when image is centered
![Llanwrst, Wales, photo by Julie Lowndes](llanwrst-wales-jslowndes.jpg){fig-align="center" width="60%" fig-alt="photo focal point is a narrow river with central sandbar, flowers in foreground along the river are dark pink and white, trees along riverside and hills in background"}

[ateucher]

This looks like a quarto bug. There is an existing issue for it for docx outputs, I added a comment for html: quarto-dev/quarto-cli#11589 (comment)

[ateucher]

Ok, apparently not a bug but by design:

"Figures" (which in the Pandoc AST are images standing alone in a paragraph with a caption) are center aligned (and their captions left-aligned, as captions are often long-ish and in that case look very strange center-aligned)

Plain images (no caption) are left aligned

Here's a discussion about it: quarto-dev/quarto-cli#2304

In short, it seems like the way to fix it is with something like:

::: {style="text-align:center;"}
![Caption text](https://quarto.org/quarto.png)
:::

[stefaniebutland]

Documented in our website wiki under Adding captions below embedded images.