Add github action for flake checks

.github/workflows/test.yml

@@ -0,0 +1,15 @@
+name: "Test"
+on:
+  pull_request:
+  push:
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - uses: cachix/install-nix-action@v31
+      - uses: cachix/cachix-action@v15
+        with:
+          name: sebastian-stork
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+      - run: nix flake check