Add option to specify output directory in quarto_render()

[JTCDCTWB]

Currently, the quarto_render() function does not have a parameter to specify the output directory for rendered files. As a result, output files (e.g., HTML, PDF, DOCX) are always generated in the same directory as the source .qmd file, which can be inconvenient for organizing projects.

It would be very helpful to add an argument like output_dir to quarto_render(), similar to rmarkdown::render(output_dir = "path/to/folder"), so that users can control where the rendered files are saved.

This would improve workflow flexibility, especially in automated or reproducible reporting pipelines.

Thank you!