initial nix flake package

[heywoodlh]

This packages hexstrike-ai as a Nix flake, making it trivial to run hexstrike with many of its dependencies that are packaged in nixpkgs.

For example, it can be run like so with my fork (i.e. in an environment without any of the recommended dependencies installed):

nix run "github:heywoodlh/hexstrike-ai/nix-flake-init"

And in a separate shell, observe that the dependencies are available to the server:

curl --silent http://localhost:8888/health | jq '.' | grep true | tail -20
    "masscan": true,
    "medusa": true,
    "nikto": true,
    "nmap": true,
    "nuclei": true,
    "nxc": true,
    "objdump": true,
    "ophcrack": true,
    "radare2": true,
    "responder": true,
    "rustscan": true,
    "sqlmap": true,
    "steghide": true,
    "strings": true,
    "subfinder": true,
    "tcpdump": true,
    "trivy": true,
    "vol": true,
    "wafw00f": true,
    "wpscan": true,

[heywoodlh]

Updated my commit with minimal docs as well as made it compatible for Nix on MacOS 😄