Page numbers on PDF Export

[liquid-metal]

Describe the feature you'd like
When exporting a page to a PDF document, it would be nice to have page numbering in the footer on the output pages.

Describe the benefits this feature would bring to BookStack users
When exporting and printing a long bookstack page (in my case 8 pages of A4 paper) it can become quite a mess if they get out of order after printing them out on paper.

[ssddanbrown]

Related to #493

[SuperPat45]

It would be useful for the table of contents to display page numbers because my book has more than 1500 pages.

I know a JavaScript library named paged.js https://pagedjs.org/documentation/ which allow this as well as complex headers, footers with page numbers...
I use it to generate full book PDF in one of my project with node.js + puppeteer module + chromium