YAML: YAML Ain’t Markup Language
http://yaml.org
YAML 语言教程
http://www.ruanyifeng.com/blog/2016/07/yaml.html
YAML 是专门用来写配置文件的语言，非常简洁和强大，远比 JSON 格式方便。
YAML SYNTAX
https://learn.getgrav.org/advanced/yaml
Learn X in Y minutes
Where X=yaml
https://learnxinyminutes.com/docs/yaml/