add cache for stocks

lib/functions/getlist_cache_function.dart

@@ -0,0 +1,20 @@
+import 'package:flutter/widgets.dart';
+import 'package:pharmacy_mobile/blocs/caches/stocklist/functions/cache_getstocklist.dart';
+
+Future<List> getListCache(BuildContext context, String type) async {
+  late final List cache;
+
+  switch (type) {
+    case 'stock':
+      cache = await cacheGetStockList(context);
+      break;
+    default:
+      return [];
+  }
+
+  if (cache.isNotEmpty) {
+    return cache;
+  } else {
+    return [];
+  }
+}