Add option to scan nix profile?

[arianvp]

I.e. it can take ~/.nix-profile/manifest.json as input

Currently you get:

% sbomnix ~/.nix-profile              
INFO     Evaluating '/Users/arian/.nix-profile'
INFO     Try force-realising store-path '/Users/arian/.nix-profile'
INFO     Loading runtime dependencies referenced by '/nix/store/pwcgic86vfhhdkpbh03cn7pv7a58vdqh-profile'
CRITICAL No deriver found for: '/nix/store/pwcgic86vfhhdkpbh03cn7pv7a58vdqh-profile