Feature request: support custom CSS file in rtoqmd()

[ddotta]

It would be very useful to be able to apply a custom CSS file when generating Quarto documents from R scripts using rtoqmd(). This would allow users to style code chunks, headings, tables, and other elements consistently without manually editing the generated .qmd file.

Proposed solution
Add a new argument, e.g. css, to the rtoqmd() function:

rtoqmd("script.R", css = "custom.css")

When provided, the CSS file should be automatically linked in the generated Quarto document.

Use case / Motivation

Consistent styling across multiple documents generated from scripts.

Ability to define a corporate or project-specific style.

Avoids having to edit the .qmd manually after generation.