feat: Auto-format Nix files using Alejandra

.github/workflows/test.yml

@@ -111,4 +111,4 @@ jobs:
         uses: ./
         with:
           nix_path: nixpkgs=channel:nixos-22.11
-      - run: nix-shell --packages cacert git nodejs pre-commit --pure --run 'pre-commit run --all-files'
+      - run: nix-shell --packages cacert git nix nodejs pre-commit --pure --run 'pre-commit run --all-files'

.pre-commit-config.yaml

@@ -2,6 +2,11 @@
 # Please run `pre-commit run --all-files` when adding or changing entries.
 
 repos:
+  - repo: https://github.com/kamadorueda/alejandra
+    rev: bb7f2ad3f176aa8e9e2944a10061f7989c8fef17 # frozen: 1.3.0
+    hooks:
+      - id: alejandra
+
   - repo: https://github.com/pre-commit/mirrors-prettier
     rev: 6f3cb139ef36133b6f903b97facc57b07cef57c9 # frozen: v3.0.0-alpha.6
     hooks: