Render supporting files for an input document
Render (copy) required supporting files for an input document to the
_files directory that is associated with the document.
render_supporting_files(from, files_dir, rename_to = NULL)
The directory from which the files should be copied.
The directory that will receive the copied files.
An option to rename the source directory after the copy operation is complete.
The relative path to the supporting files. This path is suitable
for inclusion in HTML