feat(nix): add Nix flake for NixOS support (#52)

- Suppport NixOS

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1785090369,
+        "narHash": "sha256-m0pDuRJG7EDo9ri+4Ksu83VsI+PlxNC9lNBfydejce4=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "624af665418d3c65d544145b4d34ad696439570e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,52 @@
+{
+  description = "IRIS - Shell commands suggestion tool";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
+      pkgsFor = system: nixpkgs.legacyPackages.${system};
+    in
+    {
+      packages = forAllSystems (system:
+        let
+          pkgs = pkgsFor system;
+        in
+        {
+          iris = pkgs.buildGoModule {
+            pname = "iris";
+            version = self.shortRev or "dirty";
+            src = ./.;
+
+            subPackages = [ "cmd/iris" ];
+
+            proxyVendor = true;
+            vendorHash = "sha256-kBSMhUsuCKIjAXjGfl1WSjCX+tlGi9BTnkRu9ScW6M0=";
+
+            doCheck = false;
+
+            meta = with pkgs.lib; {
+              description = "A shell auto-completion tool that works like code editor's IntelliSense";
+              homepage = "https://github.com/versenilvis/iris";
+              license = licenses.mit;
+              mainProgram = "iris";
+            };
+          };
+          default = self.packages.${system}.iris;
+        });
+
+      devShells = forAllSystems (system:
+        let
+          pkgs = pkgsFor system;
+        in
+        {
+          default = pkgs.mkShell {
+            buildInputs = with pkgs; [ go ];
+          };
+        });
+    };
+}