v1.2.3

🌟 Add

• docs/README.md: instructions for docs, provide some tool suggestions to help you quickly build your own document.
• tests/README.md: instructions for testing, provide the whole procedure of testing.
• examples/demo.ipynb: provide an example of how to demonstrate your project.

🗑️ Delete

• docs/.gitkeep
• tests/.gitkeep
• examples/.gitkeep