ci: add check and format workflows

.github/workflows/format.yaml

@@ -0,0 +1,34 @@
+name: "Format Flake"
+on:
+  push:
+    branches:
+      - main
+    paths-ignore:
+      - .github/**
+      - .gitignore
+jobs:
+  alejandra:
+    name: Format with Alejandra
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Nix
+        uses: DeterminateSystems/nix-installer-action@main
+      - name: Nix Magic Cache
+        uses: DeterminateSystems/magic-nix-cache-action@main
+      - name: Format Flake
+        run: nix run nixpkgs#alejandra -- -c .
+  deadnix:
+    name: Dead Code Analysis with Deadnix
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Nix
+        uses: DeterminateSystems/nix-installer-action@main
+      - name: Setup Deadnix
+        uses: cachix/cachix-action@v15
+        with: 
+          name: deadnix
+      - uses: astro/deadnix-action@main