added dialog for creating bookmark collections

lib/widgets/create_bookmark_collection_dialog.dart

@@ -0,0 +1,29 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+class CreateBookmarkCollectionDialog extends StatelessWidget {
+  const CreateBookmarkCollectionDialog({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return AlertDialog(
+      title: Text('Create Collection'),
+      content: TextField(
+        autofocus: true,
+        maxLines: 1,
+        maxLength: 50,
+        inputFormatters: [
+          FilteringTextInputFormatter.allow(RegExp(r'[a-zA-Z0-9äöüÄÖÜß\s]')),
+          FilteringTextInputFormatter.deny(RegExp(r'\s\s+')),
+        ],
+        decoration: InputDecoration(
+          labelText: 'Collection Name',
+          border: OutlineInputBorder(borderRadius: BorderRadius.circular(10)),
+        ),
+      ),
+      actions: [
+        FloatingActionButton(onPressed: () {}, child: Icon(Icons.save)),
+      ],
+    );
+  }
+}