docs: Add rumdl to the README

[szaffarano]

Follow-up for #664
I forgot to update the README.md file.

Update: I noticed that CI is failing due to an old nixpkgs. Not sure if you want to update it here or in another PR. It also fails with the (now deprecated) nixos 25.05, but it seems there are other failures as well

[xsteadfastx]

i hope this gets merged soon.

[szaffarano]

i hope this gets merged soon.

Hi @xsteadfastx now sure what your config is, but if using flakes, as a workaround, you could override nixpkgs, e.g.

    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";

    pre-commit-hooks = {
      url = "github:cachix/git-hooks.nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

or if you use 25.05, then define another nixpkgs input

    nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";

    pre-commit-hooks = {
      url = "github:cachix/git-hooks.nix";
      inputs.nixpkgs.follows = "nixpkgs-unstable";
    };

Hope it helps

[billf]

would use of placeholder be suitable?