longestIncreasingSubsequence.cpp and levenshteinDistance.cpp added

[sneaky-potato]

Addressed issues #7 and #9 (which were assigned to me)
@wataridori please have a look :)

[wataridori]

@sneaky-potato Thank you very much. It looks good to me 👍
However, to unify the folder structure among all Problems, could you please rename the solution files to just solution.cpp.
It means inside the Longest Increasing Subsequence Folder, we will have problem.md and solution.cpp (as well as solution.py, solution.rb ....) files

[sneaky-potato]

Ah aight, will do