bug: NixOS refuses to run the dynamically linked binary

[MatrixManAtYrService]

Maturin builds a dynamically linked binary which appears in the htty-core wheel, and NixOS refuses to run it. Users will only see the error if they pass --debug, otherwise they just see:

ht process exited with 127

[MatrixManAtYrService]

I'll add htty to nixpkgs and modify htty-core to detect NixOS and use the PATH instead of the inbuilt binary. The warning will suggest installing the nix package instead of the PyPI package (having both will work, but then one runs the risk of getting them out of sync).