adding shell.nix

shell.nix

@@ -0,0 +1,24 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  buildInputs = with pkgs; [
+    meson
+    ninja
+    pkg-config
+    gtk4
+    gtkmm4
+    libsigcxx
+    
+    # Development tools
+    gdb
+    valgrind
+    clang-tools
+  ];
+
+  shellHook = ''
+    echo "MineSweeper Development Environment"
+    echo "=================================="
+    echo "Build with: meson setup build && meson compile -C build"
+    echo "Run with: ./build/minesweeper"
+  '';
+}