nix: add flake with dev shell

flake.nix

@@ -0,0 +1,22 @@
+{
+  description = "Pterodactyl Panel";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    flake-utils,
+    ...
+  }:
+    flake-utils.lib.eachDefaultSystem (
+      system: let
+        pkgs = import nixpkgs {inherit system;};
+      in {
+        devShell = import ./shell.nix {inherit pkgs;};
+      }
+    );
+}