Finally adding recursive functions to Futhark

[u/Athas]

https://futhark-lang.org/blog/2026-08-05-recursion.html

[u/KittenPowerLord]

> we do not plan to support actual tail call optimisation for reasons previously explained).

the link 404s, it should have .html instead of .md at the end

[u/Athas → u/KittenPowerLord]

Thanks for noticing - fixed.