add solution to longest-increasing-subsequence problem - resolves #1276

[mohameddhamed]

PR Checklist:

• [ x] My submission is formatted according to the guidelines in the contributing guide
• [ x] My addition is on refer on the language README.md file
• [ x] My addition does not have a spelling problem
• [ x] My submission has a proper and user-friendly description of the algorithm
• [ x] My submission has the time complexity of the algorithm
• [ x] My submission has sample input-output of the program (NOT FOR PYTHON)

What kind of change does this PR introduce? (check at least one)

• Bugfix
• [ x] New algorithm
• Optimization in previous algorithms
• Code style update
• Refactor
• Documentation
• Other, please describe:

Briefly describe the changes in this PR

This resolves issue #1276 by providing an algorithm to the problem of Longest Increasing Subsequence in C++.

Other information:

[welcome]

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