build: add cachix, update nixpkgs and install nix action

.gitea/workflows/check-flake.yml

@@ -16,10 +16,16 @@ jobs:
       - name: Setup sudo (required for the next step)
         run: apt-get update && apt-get install -y sudo
       - name: Setup nix
-        uses: cachix/install-nix-action@v27
+        uses: cachix/install-nix-action@v30
         with:
+          extra_nix_config: |
+            experimental-features = nix-command flakes
           github_access_token: ${{ secrets.GH_ACCESS_TOKEN }}
-          nix_path: nixpkgs=channel:nixos-23.11
+          nix_path: nixpkgs=channel:nixos-24.05
+      - uses: cachix/cachix-action@v15
+        with:
+          name: palkx
+          authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
       - name: Build nix flake
         run: |
           while true; do sleep 1; rm -rf /homeless-shelter; done &