Allow wildcards in image names.

[mforbes]

Problem

Jupyter Book supports multiple image formats by allowing a wildcard in the filename fig.* which will choose from the best appropriate available image on disk.

Proposed Solution

It would be very nice if Jupyter notebooks could support this feature as well. I.e., given files like fig.png, fig.svg, and fig.pdf on disk, the following would render:

![Figure](fig.*)

<img src="fig.*"/>

etc. In the browser these would render fig.svg (probably the best? If not, fig.png) while converting to LaTeX should issue code like \includegraphics{fig} which allows LaTeX to pick the fig.pdf version.

Additional context

Inspired by CoCalc Issue #6997 which would provide a way to use their Whiteboard to generate and edit such figures.