* add doc for keypoint development

* fold examples

* some advice

* refactor doc, test=document_fix

* update yolox & yolov5, test=document_fix

* Update README_cn.md

* update doc, test=document_fix

* Update readme and pphuman readme

* Update README.md

* add data & customize, test=document_fix

* update readme

* Update README_cn.md

* Update README_cn.md

* add template, test=document_fix
Co-authored-by: NYixinKristy <576550767@qq.com>