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/devShell.nix

@@ -0,0 +1,9 @@
+{ inputsFrom ? [ ], mkShell, yt-dlp, nodejs, go }:
+mkShell {
+  inherit inputsFrom;
+  packages = [
+    yt-dlp
+    nodejs
+    go
+  ];
+}