fix: 🐛Header view hidden functionality added #299.

- In DayView, MonthView and WeekView hidden method added for hiding header.

lib/src/day_view/day_view.dart

@@ -911,3 +911,8 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
   DateTime get currentDate =>
       DateTime(_currentDate.year, _currentDate.month, _currentDate.day);
 }
+
+class DayHeader {
+  /// Hide Header Widget
+  static Widget hidden(DateTime date) => SizedBox.shrink();
+}

lib/src/month_view/month_view.dart

@@ -667,3 +667,8 @@ class _MonthPageBuilder<T> extends StatelessWidget {
     );
   }
 }
+
+class MonthHeader {
+  /// Hide Header Widget
+  static Widget hidden(DateTime date) => SizedBox.shrink();
+}

lib/src/week_view/week_view.dart

@@ -1003,3 +1003,8 @@ class WeekViewState<T extends Object?> extends State<WeekView<T>> {
   bool _showLiveTimeIndicator(List<DateTime> dates) =>
       dates.any((date) => date.compareWithoutTime(DateTime.now()));
 }
+
+class WeekHeader {
+  /// Hide Header Widget
+  static Widget hidden(DateTime date, DateTime date1) => SizedBox.shrink();
+}