update change doc (#623)

* Add files via upload

* Update README.md

* Update README.md

* Update README.md

* Delete change doc.gif

* Add files via upload

* Update README.md

* Delete change doc.gif

* Add files via upload

* Delete change doc.gif

* Add files via upload

* Update README.md

Co-authored-by: you-n-g <you-n-g@users.noreply.github.com>

Co-authored-by: you-n-g <you-n-g@users.noreply.github.com>

Author: demon143

README.md

@@ -24,8 +24,6 @@ Recent released features
 
 Features released before 2021 are not listed here.
 
-
-
 <p align="center">
   <img src="http://fintech.msra.cn/images_v060/logo/1.png" />
 </p>
@@ -398,6 +396,11 @@ This project welcomes contributions and suggestions.
 **Here are some 
 [code standards](docs/developer/code_standard.rst) when you submit a pull request.**
 
+If you want to contribute to Qlib's document, you can follow the steps in the figure below.
+<p align="center">
+  <img src="https://github.com/demon143/qlib/blob/main/docs/_static/img/change%20doc.gif" />
+</p>
+
 
 Most contributions require you to agree to a
 Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us