markdown的流程图、时序图、甘特图画法

• https://www.jianshu.com/p/a9ff5a9cdb25
• Markdown里面的序列图
• https://shd101wyy.github.io/markdown-preview-enhanced/#/diagrams?id=plantuml
• https://shd101wyy.github.io/markdown-preview-enhanced/#/zh-cn/presentation