fix: Adding documentations, tests, and amending algorithm for gcd_of_n_numbers.cpp

[hollowcrust]

Description of Change

Adding documentations, tests, and amending the algorithm to align with current guidelines.

Checklist

• Added description of change
• 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:
The current algorithm is not accurate and also does not account for 0 in the array, especially when GCD is undefined if all elements are 0.

[realstealthninja]

please unlink #2456 this does not fix the entirety of that issue. feel free to raise another issue with the name of the algorithm you intend to help update instead.

[realstealthninja]

on a side note is this for hacktober fest so i can label it as such

[hollowcrust]

Hi yes this is for Hacktoberfest. Thank you :)

[realstealthninja]

Lint this file using clang tidy

[realstealthninja]

Lgtm

[realstealthninja]

Thank you for you're contribution. A very well written pr. I will leave this up and if there is no objections will merge in a few days. Best wishes for the rest of hacktoberfest ♥️

[hollowcrust]

Thank you for you're contribution. A very well written pr. I will leave this up and if there is no objections will merge in a few days. Best wishes for the rest of hacktoberfest ♥️

Thanks!