📑 Use glossarium to support glossaries in typst

[agoose77]

This PR adds a glossary handler to the myst-to-typst package. I would like to have used the existing definitionList handling logic, but it's not possible to naively label the keys. Glossarium works around this by embedding each entry in a figure.

Right now this generates #gls("term") syntax instead of @term. This should be pretty simple to do, we just need to normalise the identifier.

This PR encodes the assumption that the identifier of a term starts with term. Can we assume this? There is a fallback in any case.

Fixes #944

[agoose77]

@rowanc1 can you remember what we concluded here about next steps?

[rowanc1]

Can we hold off on merging this for about a month? We are going to do significant work on Typst exports for SciPy in July, I would like to tackle it then.

If you want to merge in before, I think putting it behind a feature flag would be the addition I would want to see!

[agoose77]

@rowanc1 we spoke about reducing the scope of this. Now that SciPy is over, can we just merge as-is?

[rowanc1]

We are starting to build out the SciPy Typst themes now. @fwkoch merged the first of that earlier this week. Hoping will come back to this over the next few weeks!

[agoose77]

We triaged this PR as blocked during the recent weekly MyST Developers meeting. Although this functionality is useful, the format of things like glossaries is something is generally an opinionated decision. As such, we'd like to expose this to the extension system so that it can determine what this should look like. See #1801 for more.