add merge sort logic for sorting

Author: AhmedAbdoElhawary

lib/core/resources/strings_manager.dart

@@ -30,8 +30,9 @@ class StringsManager {
   static const String searching = "Searching";
   static const String sorting = "Sorting";
   static const String bubbleSort = "Bubble sort";
-  static const String selectionSort = "Selection sort";
   static const String insertionSort = "Insertion sort";
+  static const String selectionSort = "Selection sort";
+  static const String mergeSort = "Merge sort";
 
   static const String stop = "Stop";
   static const String play = "Play";

lib/features/sorting/base/view/sorting_list_page.dart

@@ -45,6 +45,14 @@ class SortingListPage extends StatelessWidget {
                   context.pushTo(Routes.selectionSort);
                 },
               ),
+              CustomRoundedElevatedButton(
+                roundedRadius: 3,
+                backgroundColor: ThemeEnum.whiteD5Color,
+                child: const RegularText(StringsManager.mergeSort),
+                onPressed: () {
+                  context.pushTo(Routes.mergeSort);
+                },
+              ),
             ],
           ),
         ),