this is a lot easier than adding footnote support for just the one instance. if a use case for footnotes appears in the future (e.g. if we wanted to render the nixpkgs manual with nixos-render-docs as well) this decision should be reevaluated.
Moved to ./contributing-to-this-manual.chapter.md. Link:
https://nixos.org/manual/nixos/unstable/#chap-contributing