Add shell nix

[no changelog]

shell.nix

@@ -0,0 +1,15 @@
+# SPDX-FileCopyrightText: 2023 Linnea Gräf <nea@nea.moe>
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+{pkgs ? import <nixpkgs> {}}:
+pkgs.mkShell {
+  buildInputs = with pkgs; [
+    bash
+    gh
+    git
+    xdg-utils
+    temurin-bin-17
+    reuse
+    pre-commit
+  ];
+}