Feature request: Page numbers and table of contents in PDF export

[arsalansufi]

Context: We prepare printed manuals from our company's digital documentation in Gitbook. We use Gitbook's PDF export function to generate a PDF, manually edit that PDF to suit our needs, and then send that PDF to a printer.

We'd love if the generated PDF included page numbers and a table of contents. The inclusion of page numbers and a table of contents could be made optional as we recognize that not everyone will want these.

Happy to provide additional information on our use case!

cc @ginvdr