Add a pretty print function

[Marusyk]

Need to extend https://github.com/Marusyk/BinaryTree/blob/master/src/BinaryTree/EnumerableExtensions.cs to add a pretty print function (like tree)

[Marusyk]

Requirement:

var binaryTree = new BinaryTree<int> { 8, 5, 12, 3, 7, 10, 15 };
binaryTree.Print();

Result

       8
    /    \
  12       5
 /  \    /  \
15  10   7   3

[AbhiAgarwal192]

@Marusyk Working on it. Will Submit a PR shortly.