BUG: Issue with PDF Generation for Julia Plots Output

[mmcky]

Describe the bug

When using Julia and the Plots.jl package the default plot mime type in ipynb json is svg+xml

The LaTeX builder doesn't know how to convert these images using sphinx.ext.imgconverter so we will need to figure out how to support these mime types either:

1. upstream in a sphinx package
2. locally converting these mime types in this package.

The preference is to focus on upstream solutions

Reproduce the bug

Build the https://github.com/QuantEcon/lecture-julia.myst project using the latex builder and the plots will be missing

List your environment

No response