Add validate_age script to other folder

[khemraj-git]

Describe your change:

This script prompts the user to input their age and validates that it's a non-negative integer.

• Written in Python
• Includes input validation and docstrings
• Useful for beginners learning control flow and input handling

Folder

Placed inside other/ folder as it doesn’t fit into existing algorithm categories.

Checklist

• Code follows Python guidelines
• Simple and beginner-friendly
• No external dependencies