[Markdown catalog] GitHub, VScode, CSDN different platforms markdown syntax toc directory

TOC1: support for GitHub, VScode, does not support the CSDN, Typora

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- [1. What is Machine Learning](#1-what-is-machine-learning)
  - [Machine Learning](#machine-learning)
  - [Supervised Learning](#supervised-learning)

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NOTE: in the directory, code may VScode widget generated automatically markdown toc

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TOC2: Support VScode, CSDN, Typora, does not support GitHub
[toc]

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TOC3: Support CSDN, does not support VScode, GitHub, Typora

@[toc](目录)