Unsupervised learning missing content

[Lola-jo]

• Mix 【open-machine-learning-jupyter-book\ml-advanced\unsupervised-learning-pca-and-clustering.md】 and 【open-machine -learning-jupyter-book\ml-advanced\unsupervised-learning.md】
• Note: The name of the file needs to be the same as the name of the file in _toc so that the file is displayed correctly
• So that the chapter 【https://press.ocademy.cc/ml-advanced/unsupervised- learning.html】 displays instructional content and visualizations (i.e., embedded html)