Added C++ solution to Maximum_Sum

[binaycodes]

Description

Added C++ solution to the question maximum sum.

Type of change

Please delete options that are not relevant.

• [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
• [x] Any dependent changes have been merged and published in downstream modules

[lizapatra220]

@binaycodes great job 👍