ci: add nix workflows

Signed-off-by: seth <getchoo@tuta.io>

.github/workflows/nix.yml

@@ -0,0 +1,44 @@
+name: Nix
+
+on:
+  push:
+    branches: ['main']
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v8
+
+      - name: Setup Nix cache
+        uses: DeterminateSystems/magic-nix-cache-action@v2
+
+      - name: Build refraction
+        run: nix build -L --fallback
+
+  check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v8
+
+      - name: Setup Nix cache
+        uses: DeterminateSystems/magic-nix-cache-action@v2
+
+      - name: Run checks
+        run: nix flake check -L --show-trace