ci: added github action for cache

.github/workflows/cachix.yml

@@ -0,0 +1,32 @@
+# Publish the Nix flake outputs to Cachix
+name: Cachix
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  publish:
+    name: Publish Flake
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@v3
+
+    - name: Install nix
+      uses: DeterminateSystems/nix-installer-action@main
+
+    - name: Setup Magic Cache
+      uses: DeterminateSystems/magic-nix-cache-action@main
+
+    - name: Authenticate with Cachix
+      uses: cachix/cachix-action@v12
+      with:
+        name: knuckles-rs
+        authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
+
+    - name: Run Checks
+      run: nix flake check -L --accept-flake-config
+
+    - name: Build nix flake
+      run: nix build -L --accept-flake-config