[Feature Request] decorator支持插槽

[hezhengxu2018]

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

目前只有component支持插槽，decorator不支持插槽。

What does the proposed API look like?

可以添加 x-decorator-content属性，具体实现类似x-content