Issues with syntax highlighting for code comments in diagram chunks

[mine-cetinkaya-rundel]

Bug description

Below are three chunks: diagram with mermaid, diagram with dots, figure with R code.

```{mermaid}
%%| echo: fenced
%%| label: fig-mermaid
%%| fig-width: 2
%%| fig-cap: A caption that contains words like use, or, and.

flowchart LR
  A[A] --> B(B)
  A[A] --> C(C)
```

```{dot}
//| echo: fenced
//| label: fig-dot
//| fig-width: 2
//| fig-cap: A caption that contains words like use, or, and.

graph G {
  layout=neato
  a -- b;
  a -- c;
}
```

```{r}
#| echo: fenced
#| label: fig-r
#| fig-width: 6
#| fig-cap: A caption that contains words like use, or, and.

plot(cars)
```

The syntax highlighting in the output is inconsistent across these chunks -- comments seem to receive highlighting like code in the diagram chunks.

quarto check Output

[✓] Checking Quarto installation......OK
      Version: 1.0.32
      Path: /Applications/quarto/bin

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.10.1
      Path: /usr/local/bin/python3
      Jupyter: 4.9.1
      Kernels: python3

[✓] Checking Jupyter engine render....OK

[✓] Checking R installation...........OK
      Version: 4.2.1
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Users/mine/Desktop/RStudio/quarto-tip-a-day/renv/library/R-4.2/x86_64-apple-darwin17.0
        - /Library/Frameworks/R.framework/Versions/4.2/Resources/library
      rmarkdown: 2.14

[✓] Checking Knitr engine render......OK

quarto tools check Output

Tool         Status            Installed     Latest  
chromium     Not installed     ---           869685  
tinytex      Up to date        v2022.07      v2022.07

• RStudio: RStudio 2022.07.0+548 "Spotted Wakerobin" Release (34ea3031089fa4e38738a9256d6fa6d70629c822, 2022-07-06) for macOS Mozilla/5.0 (Macintosh; Intel Mac OS X 12_4_0) AppleWebKit/537.36 (KHTML, like Gecko) QtWebEngine/5.12.10 Chrome/69.0.3497.128 Safari/537.36
• OS: macOS 12.4

Checklist

• formatted your issue so it is easier for us to read?
• included a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• documented the quarto version you're running, by pasting the output from running quarto check in the "Quarto Check Output" text area?
• documented the version of the quarto tools you're running, by providing the output from running quarto tools check in the "Quarto Tools Check Output" text area?
• documented the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• documented which operating system you're running? If on Linux, please provide the specific distribution as well.
• upgraded to the latest version, including your versions of R, the RStudio IDE, and relevant R packages?

[cderv]

Thanks for the report. This is indeed an improvement to make in regards with Pandoc syntax highlighter.
The highlighting syntax applied for the block is Markdown

<code class="sourceCode markdown">...</code>

• dot should be supported already by Pandoc but we are not applying it on source code chunk it seems: https://github.com/jgm/skylighting/blob/master/skylighting-core/xml/dot.xml
• mermaid syntax does not seem to be known yet in KDE which Pandoc uses (https://github.com/KDE/syntax-highlighting/tree/master/data/syntax). Supporting it would mean create a KDE theme based on other highlighting mechanism that supports it I guess.