set pref function

lib/helper/prefs.dart

+import 'package:tour_travel_agr/main.dart';
+
+const String _reimburseDate = 'rDate';
+const String _historyDate = 'hDate';
+
+String getReimburseDate() {
+  return prefs.getString(_reimburseDate) ?? '';
+}
+
+Future<void> setReimburseDate(String value) async {
+  prefs.setString(_reimburseDate, value);
+}
+
+String getHistoryDate() {
+  return prefs.getString(_historyDate) ?? '';
+}
+
+Future<void> setHistoryDate(String value) async {
+  prefs.setString(_historyDate, value);
+}