add ensure hashes workflow

.github/workflows/ensure-nix-hashes.yml

@@ -0,0 +1,30 @@
+name: Ensure Nix Hashes are up-to-date
+on:
+  push:
+  pull_request:
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install nix
+        uses: cachix/install-nix-action@v22
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - name: Update npm Hashes
+        working-directory: nix/package/web
+        shell: nix develop --command bash -c "{0}"
+        run: ./update.sh
+      - name: Update Composer Hashes
+        working-directory: nix/package
+        shell: nix develop --command bash -c "{0}"
+        run: ./update.sh
+
+      - name: Check if up-to-date
+        shell: bash
+        run: |
+          if [ "$(git status --porcelain=v1 2>/dev/null | wc -l)" = "1" ]; then
+            git status
+            echo "::error::Nix hashes are not up to date"
+          fi