feat(workflows/eval): add flake check

.github/workflows/eval-check.yml

@@ -0,0 +1,22 @@
+name: "Eval"
+
+on:
+  push:
+    branches: 'master'
+  pull_request_target:
+
+jobs:
+  check:
+    name: Check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: "actions/checkout@v4"
+      - uses: "cachix/install-nix-action@V28"
+        with:
+          nix_path: nixpkgs=channel:nixpkgs-unstable
+      - uses: cachix/cachix-action@v15
+        with:
+          name: wrangler
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+      - name: Check
+        run: nix flake check -L