Added swap(index, index1) method

Added swap method as follow:

```
/*
Swap objects at index and index1;
*/
virtual bool swap(int index, int index1);

```

```
template
bool LinkedList::swap(int index, int index1){
// Check if index position is in bounds
if(index < 0 || index >= _size)
return false;
if(index1 < 0 || index1 >= _size)
return false;

T _t = getNode(index)->data;
getNode(index)->data = getNode(index1)->data;
getNode(index1)->data = _t;
return true;
}

```

Start by locating the LinkedList class and its existing indexed-access behavior, then review how getNode and bounds checks are handled. Confirm that swap(index, index1) exchanges the two stored objects, rejects either out-of-range index, and reports success or failure consistently with the shown interface.

Written by the indexing model from the issue text.