Create time_complexity_Examples.cpp

[mariamnabeh]

Description of Change

Added a simple explanation of time complexity with a C++ example.

The file includes basic definitions of common complexity classes (O(1), O(log n), O(n), etc.) and a simple example to help beginners understand the concept.

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: Adds an educational overview of time complexity for beginners.