Math block fence for GFM with Gitlab

[Yoshinobu-Ishizaki]

I mainly use Gitlab instead of Github and want to generate Markdown file for Gitlab.

On Gitlab, math block must be fenced by $` and `$ for inline and ```math ... ``` for displayed ( See https://docs.gitlab.com/ee/user/markdown.html#math ).

This is a quick hack to generate .md file to fit well with Gitlab.

(1) Prepare with lua filter file (ex. gitlab-quarto.lua)

function Math(el)
    if el.mathtype == "InlineMath" then
        return {pandoc.RawInline("html","$`"), pandoc.RawInline("html",el.text), pandoc.RawInline("html","`$")}
    else
        return {pandoc.RawInline("html","\n\n```math"), pandoc.RawInline("html",el.text),pandoc.RawInline("html","\n```\n")}
    end
end

(2) Add YAML header

  gfm:
    html-math-method: katex
    filters: [gitlab-quarto.lua]

I use katex because Gitlab uses it.
Also, cross referencing math seems not working currently ( Codecogs does not accept \tag and generates error 😒 ) .

---

Here is a sample.

It would be nice if this feature is included officially 😄 .

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Quarto 0.9.402 , RStudiio 2022-02, R-4.1.2

[jjallaire]

I think we are overzealous w/ our use of \tag. This commit (511685e) goes back to \qquad for any scenario (including docx) which isn't mathjax or katex.