Update README.md

[eapo]

1. Separate installation scripts
2. Add NixOS shell.nix method

---

Alternatively using shell.nix (NixOS)

{ pkgs ? import <nixpkgs> { } }:

pkgs.mkShell {
  buildInputs = [
  ];
 
  shellHook =
    ''
      npx repomix --ignore "data/,ai-docs/,myenv/,.vscode/"
    '';
}

[yamadashy]

Hi, @eapo !
Thank you for your PR! I appreciate you adding installation instructions for NixOS users.

I think this is a valuable addition, but I'd like to suggest a small change to the placement. Since the shell.nix approach isn't strictly a "global installation" but rather a project-specific environment setup, it might be confusing to include it in the "Install globally for repeated use" section.

Would it be possible to create a new section titled "Using with NixOS" and place it before the "Alternative Tools 🛠️" section? This would make the README structure clearer and help users find the installation method appropriate for their environment.

A structure like this would work well:

## Using the CLI Tool `>_`

### Install globally for repeated use:
...

### Using with NixOS
For NixOS users, you can create a `shell.nix` file in your project:
...

## Alternative Tools 🛠️
...

What do you think about this organization? It clearly separates the global installation section from the NixOS usage method.

Thanks again for contributing to make Repomix more accessible to NixOS users!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.28%. Comparing base (944b1c2) to head (4e60e3d).
Report is 57 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #414   +/-   ##
=======================================
  Coverage   84.28%   84.28%           
=======================================
  Files          77       77           
  Lines        3748     3748           
  Branches      756      756           
=======================================
  Hits         3159     3159           
  Misses        589      589           

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