[Algo] Add floyd warshall algorithm for finding all pair shortest path in a connected graph [CPP]

[vivekcrux]

#287 Given the pull request.

Edit:
https://en.wikipedia.org/wiki/Floyd%E2%80%93Warshall_algorithm

[sangamcse]

GitMate.io thinks possibly related issues are #181 ([Algo] Dijkstra’s Shortest Path Algorithm [C]), #182 ([Algo] Dijkstra’s Shortest Path Algorithm [Java]), #183 ([Algo] Dijkstra’s Shortest Path Algorithm [Python]), #2 (Add all sorting algorithms), and #240 ([Algo] Optimize bubble_sort.cpp).

[paawan01]

Since the PR is closed. Is anybody working on this ?
@vivekcrux ?
if not can I be assigned on this @sangamcse ?