Feature request: Add syntax highlighting for \begin{equation}, \begin{align}, and \[...\] in .qmd files

[PatrickW-7878]

Description

The Quarto VS Code extension's TextMate grammar currently only recognizes $...$ (inline) and $$...$$ (display) as math scopes in .qmd files. LaTeX math environments like \begin{equation}, \begin{align}, and \[...\] receive no math highlighting, even though they are valid and commonly used in Quarto documents — especially in math-heavy academic papers.

Current behaviour

In a .qmd file:

• $x^2$ → highlighted as math ✅
• $$x^2$$ → highlighted as math ✅
• \begin{equation} x^2 \end{equation} → no highlighting ❌
• \begin{align} x^2 \end{align} → no highlighting ❌
• \[ x^2 \] → no highlighting ❌

Proposed solution

Add begin/end rules to quarto.tmLanguage.yaml for LaTeX math environments, scoped as markup.math.block.quarto with meta.embedded.math.quarto content — identical to how $$ blocks are handled. The change is small (~20 lines of YAML):

math_environment:
  name: markup.math.block.quarto
  contentName: meta.embedded.math.quarto
  begin: '(\\begin\{(equation|align|alignat|gather|multline|flalign|split|aligned|gathered|multlined)\*?\})'
  beginCaptures:
    '1':
      name: keyword.control.import.math.begin.quarto
  end: '(\\end\{\2\*?\})'
  endCaptures:
    '1':
      name: keyword.control.import.math.end.quarto
  patterns:
    - {include: 'text.html.markdown.math#math'}

math_display_delim:
  name: markup.math.block.quarto
  contentName: meta.embedded.math.quarto
  begin: '(\\\[)'
  beginCaptures:
    '1':
      name: keyword.control.import.math.begin.quarto
  end: '(\\\])'
  endCaptures:
    '1':
      name: keyword.control.import.math.end.quarto
  patterns:
    - {include: 'text.html.markdown.math#math'}

These rules would be added to the repository section of the grammar and included in the block patterns before math_block.

Use case

I write computational statistics papers in Quarto using \begin{equation}, \begin{align}, and custom theorem environments. The lack of math highlighting for these standard LaTeX environments makes the editing experience significantly worse compared to pure .tex files, especially for equation-heavy documents. This is likely a common pain point for anyone using Quarto for academic writing.

Happy to submit a PR if that would be helpful.