feat: add unbounded knapsack algorithm

[mrmagic2020]

Add unbounded knapsack algorithm, class dynamic_programming::unbounded_knapsack. Documentation and test cases included.

Description of Change

Checklist

• [x] Added description of change
• [x] Added file name matches File name guidelines
• [x] Added tests and example, test must pass
• [x] Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
• [x] Relevant documentation/comments is changed or added
• [x] PR title follows semantic commit guidelines
• [x] Search previous suggestions before making a new one, as yours may be a duplicate.
• [x] I acknowledge that all my contributions will be made under the project's license.

Notes:

[mrmagic2020]

@realstealthninja could you please review or dont-close? Thanks a lot!

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[github-actions[bot]]

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