feat: Added Multiplication Operator ( * ) overloads.

[HashirGJ8842]

Description of Change

Added Multiplication Operator ( ) Implementation for `largeInt intandlargeInt * int64_t` alongwith tests. Karatsuba Algorithm also fixed correctly.

Checklist

• [x] Added description of change
• [x] Proper file name given
• [x] 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
• [x] PR title follows semantic
• [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.