Allowing alternative class name

[AlbertLei]

First, thank you for creating this great filter. I am making more plots by typst because of it.

Indeed, many of my diagrams don’t use cetz at all. For example:

A diagram:

```cetz
An typst rectangle:

#rect()
```

Produces:

I’m wondering if it’s possible to use the class name typst instead of cetz for rendering diagrams? Similarly, one might prefer writing:

```tex
Math here: $y = x^2$
```

instead of

```tikz
Math here: $y = x^2$
```

This isn’t just about semantics. Users would automatically get syntax highlighting in editors that can recognize markdown/latex/typst.