Sources R files listed in `_project.yml` and from fallback folders.
load_functions(
folders = c("Rcode/function", "Rcode/00_function", "script/function",
"script/00_function")
)Invisible NULL. The function sources the R files for their side effects.
if (FALSE) { # \dontrun{
# Source all R files from default directory
load_functions()
} # }