🤔 [QUESTION] 双轴-多折线图中如何设置折线区域填充呢？

### 🐛 Question description [Please make everyone to understand it]

### 💻 Link to minimal reproduction

Please provide a link by forking these links [g2plot](https://codesandbox.io/s/g2plot-reproduction-template-gyej1) or GitHub repo. What is a minimal reproduction, and why is it required?

### 🏞 Expected result

### 🚑 Any additional [like screenshots]

* **G2Plot Version**:
* **Platform**:
* 双轴-多折线图中如何设置折线区域填充呢？
*

想实现类似如下这种效果

Start with the linked G2Plot reproduction template and inspect the dual-axis, multi-line chart configuration described in the issue. Compare its current rendering with the two screenshots and determine whether the requested filled line regions are supported; done means a reproducible configuration or a clearly scoped implementation path.

Written by the indexing model from the issue text.