Added Sum of triangular array using recursion technique

[paridhi-jain-047]

Related Issue

• Added a new file for sum of triangular array using recursion

Describe the changes you've made

I have added a new folder. Please review for the same

Type of change

[paridhi-jain-047]

I have already issued a proposal for creating a new file. But reply was not there. So, now I have created a pull request with #259 . Please let me know your review for the same. Thank you.

[paridhi-jain-047]

I have added cpp extension. And comments are already provided. Now, will it work?

[paridhi-jain-047]

Now you can merge my pull request.