Update BMI Calculate

[sulaemanahmed]

Enhanced BMI Calculation and Category Determination

• Refactored the code to improve readability and maintainability.
• Encapsulated the BMI calculation in a separate function, 'calculate_bmi'.
• Introduced a new function, 'get_bmi_category', to determine BMI category and provide recommendations.
• Updated the 'main' function to use the new functions to calculate BMI and offer recommendations.
• The code now provides a more structured and informative BMI assessment.