Add a folder containing code examples for loss and constraint sections

[BenViolet6]

Description

This PR adds a folder examples_FEI containing Jupyter notebooks. These notebooks provide code examples for each function in Loss and Constraint sections. It also includes code examples of GridSearch for SVM, Smooth SVM, and Squared SVM, as well as a separate GridSearch for Huber, MAE, and MSE

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring
• Other: Add example notebooks

Checklist

• I have tested my changes locally
• Tests pass: pytest tests/ -v
• Code follows the style guidelines (PEP 8)
• Documentation has been updated (if applicable)
• Commits are properly formatted

Additional Notes

Dear professor,

Here are all my code in the notebooks. If there is anything that needs to be improved, please let me know and I will address as quickly as possible.

[statmlben]

@BenViolet6 You may check out the documentation structure under ./doc and put the notebook in the corresponding position with proper file name. For example, some of them can put in doc/source/tutorials/loss.rst. You can check the existing format. Thx!

[BenViolet6]

@BenViolet6 You may check out the documentation structure under ./doc and put the notebook in the corresponding position with proper file name. For example, some of them can put in doc/source/tutorials/loss.rst. You can check the existing format. Thx!

Dear professor,

I have updated the PR and the details are in the email.
Thank you very much for your paitient guidance!

Best regard,
Zihang