Is your feature request related to a problem? Please describe.
I would like to add an implementation of Fenwick Tree to the Data Structures collection

Describe the solution you'd like
The data structure would be implemented using an array and would support range sum and point update queries in O(logN) time. The space complexity would be O(N) where N is the number of element of the array for which we would build the Fenwick Tree.

Additional context
https://www.geeksforgeeks.org/binary-indexed-tree-or-fenwick-tree-2/

As part of Hacktoberfest 2021, I would like to add this implementation, could you please assign this to me @cclauss , @itsvinayak
Thank you