add shell.nix for setting up devenv

shell.nix

@@ -0,0 +1,18 @@
+# https://nix.dev/tutorials/declarative-and-reproducible-developer-environments
+with import <nixpkgs> { };
+
+mkShell {
+
+  # Package names can be found via https://search.nixos.org/packages
+  nativeBuildInputs = [
+    nodejs_22
+    sqlite
+    python3
+  ];
+
+  # NIX_ENFORCE_PURITY = true;
+
+  shellHook = ''
+        export PATH="$PWD/node_modules/.bin/:$PATH"
+  '';
+}