Adds minimum impurity decrease hyper-param and a feature importance based on it

[lgmoneda]

Description

Now it has minimum impurity decrease as a possible stop criterion. The feature importance now has an option to use to total impurity decrease by variable to estimate its importance for the model.

Type of Change

• 📚 Examples / docs / tutorials / dependencies update
• 🔧 Bug fix (non-breaking change which fixes an issue)
• 🥂 Improvement (non-breaking change which improves an existing feature)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🔐 Security fix