views/month-cell: Add method for retrieving overflow button

This is needed for keyboard navigation, specifically for grabbing
focus and checking focus.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/598>

src/gui/views/gcal-month-cell.c

@@ -637,3 +637,12 @@ gcal_month_cell_set_selected (GcalMonthCell *self,
 
   gtk_widget_queue_resize (GTK_WIDGET (self));
 }
+
+GtkWidget *
+gcal_month_cell_get_overflow_button (GcalMonthCell *self)
+{
+  g_assert (GCAL_IS_MONTH_CELL (self));
+
+  return self->overflow_button;
+}
+

src/gui/views/gcal-month-cell.h

@@ -57,6 +57,8 @@ gboolean             gcal_month_cell_get_selected                (GcalMonthCell
 void                 gcal_month_cell_set_selected                (GcalMonthCell      *self,
                                                                   gboolean            selected);
 
+GtkWidget           *gcal_month_cell_get_overflow_button         (GcalMonthCell      *self);
+
 G_END_DECLS
 
 #endif /* GCAL_MONTH_VIEW_CELL_H */