Add to search.nixos.org experimental Flakes repository

[almereyda]

https://search.nixos.org/flakes?channel=25.05&query=disko has a public flakes repository, which at the moment does not list Disko.

It would have saved me a great deal of time knowing that Disko existed and that I could use it for my Nix partitioning needs.

The repository is on GitHub itself.

• https://github.com/NixOS/nixos-search/blob/main/flakes/manual.toml

Would there be opposition to a PR against that repository for increasing visibility of disko, disko-install and its integration with nixos-anywhere? (Which is also not listed there.)