flake-compat not present in flake.lock

[bsima]

The description in the readme about how to use with niv does not work because flake-compat is not in your lock file:

   error: attribute 'flake-compat' missing                           
                           
   at /nix/store/7fijhv3dkfcad40adlfb0ibk0n4d3xnr-mynixpkgs-src/flake-compat.nix:7:12:                                                         
                           
        6|   lock = builtins.fromJSON (builtins.readFile flakeLockPath);                                                                       
        7|   inherit (lock.nodes.flake-compat.locked) owner repo rev narHash;                                                                  
         |            ^  
        8|