add nix package

linux/nix/package.nix

@@ -1,39 +0,0 @@
-{
-  lib,
-  libclang,
-  flutter,
-  src,
-  go,
-}:
-
-flutter.buildFlutterApplication {
-  pname = "nexus";
-  version = "0.1.0";
-  inherit src;
-
-  preBuild = ''
-    packageRunCustom nexus generate source/scripts test
-    packageRun build_runner build
-  '';
-
-  env.LIBCLANG_PATH = lib.makeLibraryPath [ libclang ];
-
-  nativeBuildInputs = [
-    go
-  ];
-
-  autoPubspecLock = src + "/pubspec.lock";
-
-  gitHashes = {
-    window_size = "sha256-XelNtp7tpZ91QCEcvewVphNUtgQX7xrp5QP0oFo6DgM=";
-    flutter_chat_ui = "sha256-4fuag7lRH5cMBFD3fUzj2K541JwXLoz8HF/4OMr3uhk=";
-    flutter_link_previewer = "sha256-4fuag7lRH5cMBFD3fUzj2K541JwXLoz8HF/4OMr3uhk=";
-  };
-
-  meta = {
-    description = "A simple and user-friendly Matrix client";
-    mainProgram = "nexus";
-    platforms = lib.platforms.linux;
-    maintainers = with lib.maintainers; [ quadradical ];
-  };
-}