change the image path instead of hosting in github

Currently we use the code snippet as below to zoom the image
```
<p align="center">
    <img src="https://raw.githubusercontent.com/byzer-org/byzer-doc/main/kolo-lang/zh-cn/introduction/images/register.png" alt="name"  width="800"/>
</p>
```

it uses the image absolute path in github.

But in china, the network can not access the githubusercontent, we need to find another way