Add basic Nix flake

drupal-cms/flake.nix

@@ -0,0 +1,25 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+  };
+
+  outputs =
+    inputs:
+    let
+      system = "x86_64-linux";
+      pkgs = import inputs.nixpkgs { inherit system; };
+    in
+    {
+      devShells.${system}.default = pkgs.mkShell {
+        packages = with pkgs; [
+          (php.buildEnv {
+            extraConfig = ''
+              memory_limit = 512M
+            '';
+          })
+
+          sqlite
+        ];
+      };
+    };
+}