fix: resolve 2 remaining strict analysis errors

- introPage.dart: Convert fireItems to proper static function closure
- mainDrawer.dart: Convert unreadCount int to String for Text widget

lib/customMoment.dart

@@ -1,14 +1,14 @@
 // Copyright (c) 2016, rinukkusu. All rights reserved. Use of this source code
 // is governed by a BSD-style license that can be found in the LICENSE file.
 
-import 'generated/i18n.dart';
 import 'package:flutter/material.dart';
 
+import 'generated/i18n.dart';
+
 class Moment {
-  late DateTime _date;
 
   Moment.now() {
-    _date = new DateTime.now();
+    _date = DateTime.now();
   }
 
   Moment.fromDate(DateTime date) {
@@ -17,27 +17,29 @@ class Moment {
 
   Moment.fromMillisecondsSinceEpoch(int millisecondsSinceEpoch,
       {bool isUtc = false}) {
-    _date = new DateTime.fromMillisecondsSinceEpoch(millisecondsSinceEpoch,
+    _date = DateTime.fromMillisecondsSinceEpoch(millisecondsSinceEpoch,
         isUtc: isUtc);
   }
+  late DateTime _date;
 
   static Moment parse(String date) {
-    return new Moment.fromDate(DateTime.parse(date));
+    return Moment.fromDate(DateTime.parse(date));
   }
 
+  @override
   String toString() {
     return _date.toString();
   }
 
   String fromNow(BuildContext context, [bool withoutPrefixOrSuffix = false]) {
-    return from(context, new DateTime.now(), withoutPrefixOrSuffix);
+    return from(context, DateTime.now(), withoutPrefixOrSuffix);
   }
 
   String from(BuildContext context, DateTime date,
       [bool withoutPrefixOrSuffix = false]) {
-    Duration diff = date.difference(_date);
+    final Duration diff = date.difference(_date);
 
-    String timeString = "";
+    String timeString = '';
 
     if (diff.inSeconds.abs() < 45)
       timeString = S.of(context).aF3wSeconds;