add flake environment

flake.nix

@@ -0,0 +1,64 @@
+{
+  description = "devshell-shfx";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+  };
+
+  outputs = inputs @ {
+    self,
+    nixpkgs,
+  }: let
+    defaultSystems = ["aarch64-darwin" "aarch64-linux" "i686-linux" "x86_64-darwin" "x86_64-linux"];
+
+    forAllSystems = f:
+      nixpkgs.lib.genAttrs defaultSystems (system:
+        f system (import nixpkgs {
+          inherit system;
+          overlays = builtins.attrValues self.overlays;
+        }));
+  in {
+    overlays.default = final: prev: {
+      shfx = final.buildNimPackage (finalAttrs: {
+        pname = "shfx";
+        version = "0.0.1";
+
+        src = final.fetchFromGitea {
+          domain = "forge.imbored.dev";
+          owner = "emileclarkb";
+          repo = finalAttrs.pname;
+          rev = "9d04e47161219b4cd2d7f732bb9a40a25e5c93e5";
+          hash = "sha256-d3gl38/5W2WWsYpRZ/TDNo2bpgVZvpuc/2yvVpvWQxI=";
+        };
+
+        nimRelease = true;
+
+        nimbleFile = ./shfx.nimble;
+        lockFile = ./lock.json;
+
+        nimFlags = ["-d:NimblePkgVersion=${finalAttrs.version}"];
+      });
+    };
+
+    devShells = forAllSystems (
+      system: pkgs: {
+        default = pkgs.mkShell {
+          packages = with pkgs; [
+            nim
+            nimble
+
+            shfx
+          ];
+
+          shell = "${pkgs.bash}/bin/bash";
+        };
+      }
+    );
+
+    checks = self.packages;
+    packages = forAllSystems (system: pkgs: rec {
+      default = shfx;
+      shfx = pkgs.shfx;
+    });
+  };
+}