Eleventy (AKA 11ty) is a static site generator for JavaScript. I like it becuase it allows you to mix and match different template engines (hbs, nunjucks, liquid, markdown), even in the same file.
This file is a hbs (Handlebars) file so I am writing HTML-ish code right now, but I can also access template variables if I've created any. I don't have much here but I could show the page url:
/slides/1/A footer could go here.