Add the definition of DAO to the glossary

[jackleeio]

Describe the feature or improvement 描述新特性或改进

Add the definition of DAO to the glossary

Optional: Affected page(s) or section(s) 受影响的页面

https://www.confluxdocs.com/docs/general/conflux-basics/glossary

Optional: Why is this feature or improvement important? 为什么需要这个新特性或改进？

No response

Optional: Implementation ideas 如何实现

No response

Optional: Additional context 其他上下文信息

No response

Contribution Confirmation

• I'd be willing to contribute this feature myself within 2 months. 我将在两个月内自己实现这个feature