Added spiral_traversal_of_binary_tree cpp file

[Aniketraj05]

Contributing to hacktoberfest 2021 please accept or add a label hactoberfest-accepted Thanks Spiral traversal of Binary tree is implemented using two different approach. One is Naive approach and other is efficient method. Link to the problem is : - https://www.geeksforgeeks.org/level-order-traversal-in-spiral-form/

[mihir0699]

Please follow the guidelines mentioned in the readme