Added InterviewBit Max Sum Contiguous Subarray C++ and Readme.md file

[CSAURABH]

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• [x] My Pull Request adheres to the Contribution guidelines.
• [x] I have added readme.md and solution files in the appropriate folder
• [x] None of the folder and file names I have added contain any invalid characters, leading digits or trailing whitespaces
• [x] The solution I have given is my own and not plagiarized in any form.
• [x] My solution passes all the testcases.
• [x] I have properly indented and documented my solution using comments.

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[CSAURABH]

@Vishruth-S Please Review my pull request.

[mergify[bot]]

Hey there, looks like there are some conflicting files. Please resolve the conflicts so that your Pull Request can be reviewed.