🤔 [QUESTION] package.json中的sideEffects字段缺失，导致tree shaking失效

### 🐛 Question description [Please make everyone to understand it]
请问为什么package.json中的sideEffects字段没有了，导致不能使用tree shaking了，在之前的changelog 2.3.20 (2021-05-13) 中是添加了这个字段的，

commit地址： https://github.com/antvis/g2plot/commit/7f4cd17dfeb430534e660e1902009c83e349b71c

### 🏞 Expected result
支持tree shaking

### 🚑 Any additional [like screenshots]

* **G2Plot Version**: 2.4.7
* **Platform**: mac

Start by inspecting package.json in the v2.4.7 tree and comparing it with commit 7f4cd17dfeb430534e660e1902009c83e349b71c. Check the package metadata and build output for tree-shaking behavior; done means the published package supports tree shaking as expected.

Written by the indexing model from the issue text.