Add minimal local Rust example

[malteneuss]

I'm trying to package a small Rust project within NixOS and really like that just works (build and package) with minimal Nix code.

Having tried dream2nix (Rust within NixOS in general) for the first time i believe a minimal, local Rust example would have helped me a lot. I would like to add PR with such an example project with some explanation. Would a small hello-world example like the following be ok?

# flake.nix
{
  description = "Minimal Rust dream2nix example";
  inputs = {
      nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
      dream2nix.url = "github:nix-community/dream2nix";
      dream2nix.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = { self, nixpkgs, lib, dream2nix }:
        dream2nix.lib.makeFlakeOutputs {
              systems = ["x86_64-linux"];
              config.projectRoot = ./.;
              source = lib.sourceFilesBySuffices ./. [
                  ".rs"
                  "Cargo.toml"
                  "Cargo.lock"
              ];
              projects."rust-dream2nix" = {
                  name = "rust-dream2nix";
                  translator = "cargo-lock";
              };
              # With Rust workspaces better run auto-detection
              # "nix run github:nix-community/dream2nix#detect-projects ."
              # to generate a `projects.toml` file to reference here:
              # projects = ./projects.toml;
        };
}

# projects.toml
[rust-dream2nix]
name = "rust-dream2nix"
translator = "cargo-lock"
# optional settings
# subsystem = "rust"
# relPath = ""
# translators = [ "cargo-lock", "cargo-toml",]
# builder = "crane"

1. If ok, should this be an example with its own folder in https://github.com/nix-community/dream2nix/tree/main/examples, or be listed in the docs https://nix-community.github.io/dream2nix/subsystems/rust.html?
2. What is the name in projects.toml for? At least with a single Rust project (no workspace) i have to set it, but it seems the value can be anything.
3. Also i've seen some example using fennix. When would that be useful, since crane (the current default builder) seems to be working fine.
4. What is an IFD and why is that an issue? An explanation or better a link in the Rust section to a beginner-friendly explanation would be good (i could add that).