Docs, Tests, Fix: Fit fibonacci_large.cpp to contributing guideline

[setbit123]

Description of Change

Fit fibonacci_large.cpp to contributing guideline.
Try to solve a small portion of the issue #2456

Checklist

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

Notes:

[github-actions]

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