email: style images with captions

Bug description

Given the Quarto document:

---
title: customized
format: email
---

Not the message.

::: {.email}

::: {.subject}
The subject.
:::

The message.

![Quarto](quarto.png){}

Trailing text.
:::

with the quarto.png.

When rendered, the image is given a figure caption, which causes the indentation of that image, but the email format could style that image and its caption rather than letting it look like the remainder of the message text.

Note: If this is an intentional choice, please feel free to close this issue as working-as-expected.

Steps to reproduce

Render the described project and look at the HTML in the email-preview and/or the rsc_email_body_html field of the .output_metadata.json file.

Expected behavior

A figure with a styled caption.

Actual behavior

Default style for captions.

Your environment

No response

Quarto check output

Quarto 1.4.549
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.11: OK
      Dart Sass version 1.69.5: OK
      Deno version 1.37.2: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.4.549
      Path: /Applications/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/aron/Library/TinyTeX/bin/universal-darwin
      Version: 2022

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.11.7
      Path: /usr/local/opt/python@3.11/bin/python3.11
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with python3 -m pip install jupyter

[✓] Checking R installation...........OK
      Version: 4.3.1
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/4.3-x86_64/Resources/library
      knitr: 1.45
      rmarkdown: 2.25

[✓] Checking Knitr engine render......OK