add github action to build & cache steamdeck home-manager config

.github/workflows/nix-build.yaml

@@ -25,6 +25,24 @@ jobs:
   #         authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
   #     - run: nix build .#devShells.x86_64-linux.default --print-build-logs --impure
 
+  # system & home configurations
+  home-deck:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v25
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      - uses: cachix/cachix-action@v14
+        with:
+          name: gabedunn
+          # If you chose signing key for write access
+          signingKey: "${{ secrets.CACHIX_SIGNING_KEY }}"
+          # If you chose API tokens for write access OR if you have a private cache
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+      - run: nix build '.#homeConfigurations."gabe@deck".activationPackage'
+      - run: nix-shell --run "echo OK"
+
   packages-beekeeper:
     runs-on: ubuntu-latest
     steps: