function to easily add a preamble in R file for script rendering

[cderv]

Rendering R script is possible in 1.4 now, but quarto does require a YAML preamble for it to be considered a script to be rendered

https://quarto.org/docs/computations/render-scripts.html#knitr

We could add a simple function in this package to easily add it, and default the title to be the name of the file (same default as spinning)

quarto::add_spin_preamble("script.R")

would add

#' ---
#' title: script.R
#' ---

at the very top of the file

This would allow to easily batch process folder of file using a looping function