[C++] Extract Concepts from v2 exercise: food-chain

[silvanocerza]

Extract the list of concepts required to solve the v2 C++ exercise: food-chain. For each concept, describe why it is required to solve the exercise. Keep in mind that an exercise can have multiple approaches (you can find community solutions here: https://exercism.io/tracks/cpp/exercises/food-chain/solutions). The goal of this task is to help determine the total list of concepts that make up food-chain.

The list of concepts should be stored in the following document: languages/cpp/reference/exercise-concepts/food-chain.md. Use this link to create a PR to add this document.