Feature request: fragment-index for code-line-numbers

One possibility to address the problem of setting fragment order easily in Rmarkdown for code-line-numbers, discussed here:

https://github.com/hakimel/reveal.js/issues/3055#issuecomment-1477534636

Include a new option #| fragment-index: ""

```{r, echo=T}
#| fragment-index: "0"
#| code-line-numbers: "|1|2|3"
x <- 1:10
x
LETTERS[x]
```

This would set the "start" index of the first code highlighting fragment, which would already solve my use case, which would be going through code in one chunk with highlight fragments in one column, after all those fragments showing the plot output as a fragment in the second column and then displaying some text fragment in the first column below the code chunk.

Start by tracing how R Markdown options for code-line-numbers are passed into the reveal.js output, using the linked reveal.js discussion for the intended fragment ordering. Confirm how a fragment-index value should affect the first highlighting fragment and verify the example produces the requested sequence across code, plot, and text fragments.