Add Convex Hull in C++

[matterwoven]

Project name: ConvexHull
Project link: https://sampleprograms.io/projects/convex-hull/
Language: C++

The project link must be a link to a project on the Sample Programs Website project list.
If you would like to add a new project to the Sample Programs Website,
please first make a pull request to the Sample Programs Website.

[rzuckerm]

@matterwoven , you are assigned. Please make sure to read the Contributing Document if you have not done so already.