Create a new Symfony project

Using `symfony new` and Build Configs.

Signed-off-by: Oliver Davies <oliver@oliverdavies.uk>

symfony/flake.nix

@@ -0,0 +1,20 @@
+{
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+
+  outputs = inputs:
+    let
+      system = "x86_64-linux";
+      pkgs = import inputs.nixpkgs { inherit system; };
+    in
+    {
+      devShells.${system}.default =
+        with pkgs;
+        mkShell {
+          buildInputs = [
+            php
+            phpPackages.composer
+            symfony-cli
+          ];
+        };
+    };
+}