Add Colab Examples, Update Readme

[MooooCat]

Description

Add Colab Examples:

• LLM: Data Synthesis
• LLM: Off-table Feature Inference
• CTGAN

Update Readme:

• examples
• wechat group QR code

Motivation and Context

How has this been tested?

Types of changes

• Maintenance (no change in code, maintain the project's CI, docs, etc.)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.82%. Comparing base (54ee09b) to head (2c7253b).

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #147   +/-   ##
=======================================
  Coverage   79.82%   79.82%           
=======================================
  Files          69       69           
  Lines        3252     3252           
=======================================
  Hits         2596     2596           
  Misses        656      656           

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