feat(setup): add nix build instructions

This creates a binary that can be used on NixOS.

Author: lh-lasse-haffke

flake.lock

@@ -0,0 +1,25 @@
+{
+  description = "auto-doc: Github action that turns your reusable workflows and custom actions into easy to read markdown tables.";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-24.11";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+  }: let
+    system = "x86_64-linux";
+  in {
+    packages.x86_64-linux.auto-doc = nixpkgs.legacyPackages.${system}.buildGoModule {
+      pname = "auto-doc";
+      version = "3.6.0";
+
+      src = ./.;
+      vendorHash = "sha256-kO5xCO8bjs2vF4CS35odlhz17jPcpvQ6gdrE61p7x/w=";
+      doCheck = false;
+    };
+
+    packages.x86_64-linux.default = self.packages.x86_64-linux.auto-doc;
+  };
+}