Add cachix

Author: InfinityGhost

.github/workflows/nix.yml

@@ -13,5 +13,9 @@ jobs:
       with:
         extra_nix_config: |
           access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+    - uses: cachix/cachix-action@v12
+      with:
+        name: opentabletdriver
+        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
     - run: nix build
     - run: nix flake check