Add magic nix cache

Author: njaremko

.github/workflows/deploy.yml

@@ -7,6 +7,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
       - uses: cachix/cachix-action@v14
         with:
           name: nix-community