C++ solution to Product_finder

[heisenberg070]

Description

Added C++ solution for the question product_finder

Type of change

• [x] New feature (non-breaking change which adds functionality)
• [x] This change requires a documentation update

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have made corresponding changes to the documentation

[ZekromRND]

@heisenberg070 Good Job 👍