feat (home/shell): update alias

shells/why3/flake.nix

@@ -0,0 +1,31 @@
+{
+  description = "Why3 nix-flake devshell.";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+  };
+
+  outputs =
+    { self, nixpkgs, ... }:
+    let
+      system = "x86_64-linux";
+    in
+    {
+      devShells."${system}".default =
+        let
+          pkgs = import nixpkgs { inherit system; };
+        in
+        pkgs.mkShell {
+          packages = with pkgs; [
+            why3
+            alt-ergo
+            z3
+            cvc5
+          ];
+
+          shellHook = ''
+            why3 config detect
+          '';
+        };
+    };
+}