ci: Add nix workflow

.github/workflows/nix-flake.yml

@@ -0,0 +1,25 @@
+name: Nix Build 
+
+on:
+  pull_request:
+  push:
+    branches: ["*"]
+  workflow_dispatch:
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: "write"
+      contents: "read"
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@main
+        with:
+          extra-conf: accept-flake-config = true
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - uses: DeterminateSystems/flake-checker-action@main
+      - name: Build default package
+        run: nix build .
+      - name: Check flakes
+        run: nix flake check --allow-import-from-derivation