gitbook: The GitBook output format
In bookdown: Authoring Books and Technical Documents with R Markdown

This output format function ported a style provided by GitBook (https://www.gitbook.com) for R Markdown.

gitbook(
  fig_caption = TRUE,
  number_sections = TRUE,
  self_contained = FALSE,
  lib_dir = "libs",
  pandoc_args = NULL,
  ...,
  template = "default",
  split_by = c("chapter", "chapter+number", "section", "section+number", "rmd", "none"),
  split_bib = TRUE,
  config = list(),
  table_css = TRUE
)

`fig_caption, number_sections, self_contained, lib_dir, pandoc_args`	... Arguments to be passed to `rmarkdown::html_document()` (`...` not including `toc`, and `theme`).
`...`	Other arguments to be passed to `base_format`. For `html_book()` and `tufte_html_book()`, `...` is passed to `html_chapters()`.
`template`	Pandoc template to use for rendering. Pass `"default"` to use the bookdown default template; pass a path to use a custom template. The default template should be sufficient for most use cases. In case you want to develop a custom template, we highly recommend to start from the default template: https://github.com/rstudio/bookdown/blob/master/inst/templates/gitbook.html.
`split_by`	How to name the HTML output files from the book: `rmd` uses the base filenames of the input Rmd files to create the HTML filenames, e.g. generate ‘chapter1.html’ for ‘chapter1.Rmd’; `none` means do not split the HTML file (the book will be a single HTML file); `chapter` means split the file by the first-level headers; `section` means the second-level headers. For `chapter` and `section`, the HTML filenames will be determined by the header ID's, e.g. the filename for the first chapter with a chapter title `# Introduction` will be ‘introduction.html’; for `chapter+number` and `section+number`, the chapter/section numbers will be prepended to the HTML filenames, e.g. ‘1-introduction.html’ and ‘2-1-literature.html’.
`split_bib`	Whether to split the bibliography onto separate pages where the citations are actually used.
`config`	A list of configuration options for the gitbook style, such as the font/theme settings.
`table_css`	`TRUE` to load gitbook's default CSS for tables. Choose `FALSE` to unload and use customized CSS (for exmaple, bootstrap) via the `css` option. Default is `TRUE`.