[FEATURE] Distribute the CLI as a NixOS package

[edenreich]

Summary

To be more flexible in addition to a simple curl installer adding the CLI as a NixOS package will allow better versioning and convenient installer.

Acceptance Criteria

• The CLI can be installed via nix shell
• The CLI can be installed via flox
• It's documented
• It's tested

[edenreich]

Initial Pull Request is made to the NixOS pkgs repo: NixOS/nixpkgs#513418