Sorry if this post is trivial for most of people here, but it turns out that it’s not super easy to find documentation on the internet on how to quickly run in software that is written in haskell, and that is already available online. It turns out that it is pretty simple, just do:
$ nix-shell -p haskellPackages.hakyll
and then you can use the program using:
$ hakyll-init yourwebsite
I don’t know why, but it turns out that a search (at least with flake's version) does not show up that kind of packages:
$ nix search nixpkgs hakyll
error: --- Error --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- nix
no results for the given search term(s)!