Add Nix (#177)

* add Nix support

* fix formatter output

* mention Nix in README

* fix common import

* fix frontend old version import

* clarified flake pkgs order

* rm old dataDir option

* comment typo

* fix password assertion

* rm old User/Group logic

* rewrite assertion boolean expr

* General flake touchup

- Rewrite `callPackage` exprs to be more readable
- Add pre-commit support for devShell
- Add direnv support

* add simple test

* use correct test func

nix/frontend.nix

@@ -0,0 +1,37 @@
+{ lib
+, stdenv
+, nodejs
+, pnpm
+}:
+let common = import ./common.nix { inherit lib; }; in
+stdenv.mkDerivation (finalAttrs: {
+  pname = "yt-dlp-web-ui-frontend";
+
+  inherit (common) version;
+
+  src = lib.fileset.toSource {
+    root = ../frontend;
+    fileset = ../frontend;
+  };
+
+  buildPhase = ''
+    npm run build
+  '';
+
+  installPhase = ''
+    mkdir -p $out/dist
+    cp -r dist/* $out/dist
+  '';
+
+  nativeBuildInputs = [
+    nodejs
+    pnpm.configHook
+  ];
+
+  pnpmDeps = pnpm.fetchDeps {
+    inherit (finalAttrs) pname version src;
+    hash = "sha256-NvXNDXkuoJ4vGeQA3bOhhc+KLBfke593qK0edcvzWTo=";
+  };
+
+  inherit (common) meta;
+})