Try to cache the eleventy build step

.gitea/workflows/build-and-copy.yaml

@@ -14,6 +14,12 @@ jobs:
           node-version: 20.x
       - name: Install dependencies 📦
         run: npm ci
+      - name: Cache build
+        id: cache-eleventy-build
+        uses: actions/cache@v4
+        with:
+          path: .cache
+          key: cache-eleventy-build
       - name: Build eleventy
         run: npm run build
         env: