Keep the intermediate tex file used in the conversion to PDF
citation_package
The LaTeX package to process citations, natbib
or biblatex. Use none if neither package is to be used.
base_format
The function to use for the base format of the article.
By default, this is rmarkdown::pdf_document, but to use bookdown's
cross-referencing feature, this can be set to bookdown::pdf_document2