Add shimmer loading

lib/screens/wool.dart

@@ -1,8 +1,10 @@
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
+import 'package:shimmer/shimmer.dart';
 import 'package:temperaturdecke/database.dart';
 import 'package:temperaturdecke/screens/add_wool_modal.dart';
 import 'package:temperaturdecke/widgets/cards/wool_card.dart';
+import 'package:temperaturdecke/widgets/custom_card.dart';
 
 class WoolScreen extends StatelessWidget {
   WoolScreen({super.key});
@@ -16,8 +18,34 @@ class WoolScreen extends StatelessWidget {
           .get(),
       builder: (BuildContext context, AsyncSnapshot snapshot) {
         if (snapshot.connectionState == ConnectionState.waiting) {
-          return const Center(
-            child: CircularProgressIndicator(),
+          return Center(
+            child: Shimmer.fromColors(
+              baseColor: Theme.of(context).colorScheme.secondaryContainer,
+              highlightColor: Theme.of(context)
+                  .colorScheme
+                  .onSecondaryContainer
+                  .withOpacity(.3),
+              child: ListView.builder(
+                itemBuilder: (BuildContext context, int index) {
+                  return Padding(
+                    padding: const EdgeInsets.symmetric(horizontal: 10),
+                    child: Column(
+                      children: [
+                        CustomCard(
+                          SizedBox(
+                            height: 70,
+                          ),
+                        ),
+                        const SizedBox(
+                          height: 15,
+                        )
+                      ],
+                    ),
+                  );
+                },
+                itemCount: 6,
+              ),
+            ),
           );
         } else {
           // Hier können Sie den Inhalt basierend auf den geladenen Daten anzeigen