Create hangingmangm.cpp

[x] Added description of change
[x] Added file name matches File name guidelines
[x] Added tests and example, test must pass
[x] Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
[x] Relevant documentation/comments is changed or added
[x] PR title follows semantic commit guidelines
[x] Search previous suggestions before making a new one, as yours may be a duplicate.
[x] I acknowledge that all my contributions will be made under the project's license.

Notes:

TheAlgorithms / C-Plus-Plus