## Use `${` and `}$` for math fencing in Markdown documents instead

### Description

Just had a thought about Markdown math fencing...

Similar issue to #29086:-

GitLab currently uses `$`e^x`$`

for inline math and fenced code block with language id `math`

for block math:

```
```math
\int e^t dt
```
```

Neither of these syntaxes is supported by external Markdown editors or the original LaTeX language by default. This means that these documents only display correctly on GitLab.

I am thankful that GitLab thought about how to support mathematics in markdown on site, and I believe that much effort went into the deliberation. This is a tough issue because converting pure `$`

pair into LaTeX will result in much false positive, yet `(`

, `[`

& `{`

type of parenthesis were already heavily used in usual text fencing. We will most likely need 2-characters at least to do proper fencing that does not result in false positive. `\(`

, `\[`

, and `\\(`

etc were proposed but they 1.) do have false positive, e.g. with regex, and 2.) are not supported by the original LaTeX specification.

### Proposal

Fence inline math with `${`

and `}$`

pair for inline math, and fence block math with `$${`

and `}$$`

. For example `${\alpha}$`

will render in LaTeX. Notice that such fencing will render correctly in native LaTeX too as the curly-braces are treated as grouping and ignored.

I believe with a quick search through GitLab & GitHub repos that there isn't much documents with these symbols. It will be good to quickly reserve them for Markdown math usage so that the world can start typing math with code =)