Update cachix/cachix-action action to v15 (#98)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/cachix.yml

@@ -18,7 +18,7 @@ jobs:
     - uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixos-unstable
-    - uses: cachix/cachix-action@v14
+    - uses: cachix/cachix-action@v15
       with:
         name: davegallant
         authToken: '${{ secrets.CACHIX_API_KEY }}'

machines/hephaestus/configuration.nix

@@ -94,6 +94,7 @@ in
       iputils
       kazam
       legendary-gl
+      libation
       lm_sensors
       mullvad-vpn
       netdata