Catboost regressor

[AHuzail]

Add CatBoost Regressor Example

[x] Added Algorithm

Changes:

• Added a Python script catboost_regressor.py that implements a CatBoost Regressor using the California Housing dataset.
• Included doctests to validate the data_handling and catboost_regressor functions.
• Used Mean Squared Error (MSE) to evaluate model performance.

Doctests:

• Included for data_handling() and catboost_regressor() functions.

Dependencies:

• catboost, scikit-learn, numpy

Example Output:

Mean Squared Error on Test Set: <calculated_value>