feat:add graycode algorithm

[Harshdev098]

Description of Change:- added a gray code algorithm in bit manipulation folder, its a Function to generate Gray code sequence for 'n' bits.

Checklist

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

Notes:

[github-actions[bot]]

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