Fix collapsed inline math blocks

[A-Walrus]

Fixes #69.
Calculate the width and height manually instead of relying on clientHeight/clientWidth which don't work on hidden elements.

[michihupf]

Is there any reason this has not been merged yet? I have tried and failed to build your repo (@A-Walrus) from source as not having reliable rendering in callouts makes this plugin unusable for me.

The code seems clear enough, no merge conflicts...

[VincentTam]

I've just merged this PR on top of mine, and I can say that is plugin almost solves the linked issue.

The typst interpretation inside the codeblock and inline math mode is correct. However, inside a collapsible display math mode marked by $$…$$, != didn't get interpreted into ≠ unless I put it inside a typst codeblock.

File that I used for testing:

Typst code blocks:

> [!note]- Secret facts
> $1 + 2 = 3$
> $$a + b != c$$
> ```typst
> #import "@preview/cetz:0.3.1"
> 
> Hello World
> 
> Hi this is Vin
> $
> sum_(i=1)^n 1/2^i != 1 - 1/2^n.
> $
> 
> #cetz.canvas({
>   import cetz.draw: *
> 
>   grid((-1.5, -1.5), (1.4, 1.4), step: 0.5, stroke: black + 0.2pt)
> })
> ```

Display math blocks:
> [!note]- Secret facts
> $$1 + 1 = 2$$, but $$1 + 2 != 2$$.

Expanded by default:
> [!note]+ Secret facts
> $1 + 1 = 2$, but $1 + 2 != 2$.