Add shell.nix

shell.nix

@@ -0,0 +1,12 @@
+{pkgs ? import <nixpkgs> {}}: let
+  dotnet = with pkgs.dotnetCorePackages;
+    combinePackages [
+      sdk_7_0
+      aspnetcore_7_0
+    ];
+in
+  pkgs.mkShell {
+    packages = [dotnet];
+
+    DOTNET_ROOT = "${dotnet}";
+  }