Add ConvertTime Class with Time Conversion Functionality and Unit Tests

[arafat-web]

Description:
This pull request introduces the ConvertTime class, providing a robust time conversion function alongside a complete suite of unit tests to ensure accurate and reliable operation.

Key Features:

• convertTime Function: Converts a specified value between various time units (e.g., seconds, minutes, hours, days, weeks, months, and years) using predefined conversion factors.
• Exception Handling: Throws clear exceptions for invalid input units, enhancing user feedback and preventing errors.
• PSR-12 Compliance: The code adheres to PSR-12 standards, ensuring readability and maintainability.

Unit Tests:

The ConvertTimeTest class covers the following:

• Basic Conversion Tests: Verifies correct conversions between time units.
• Edge Case Handling: Tests zero-value conversions for non-negative results.
• Invalid Unit Handling: Tests exception handling for invalid from and to units with descriptive error messages.

This addition enhances functionality by enabling easy and accurate time conversions while ensuring reliability through comprehensive testing.