Add a basic nix flake for development (#6531)

* feat: add a basic nix flake

* fix: dev server on nixos

.gitignore

@@ -16,3 +16,8 @@ config.json
 # vim
 *.sw?
 
+# direnv
+.direnv/
+
+# environment related
+.envrc

flake.nix

@@ -0,0 +1,34 @@
+{
+  description = "jellyfin-web nix flake";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs";
+    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 = with pkgs;
+          mkShell rec {
+            buildInputs = [
+              nodejs_20
+            ];
+
+            shellHook = ''
+              # Also see: https://github.com/sass/embedded-host-node/issues/334
+              echo "Removing sass-embedded from node-modules as its broken on NixOS."
+              rm -rf node_modules/sass-embedded*
+            '';
+          };
+      }
+    );
+}