Chunk.entrypoints: Use Chunks.groupsIterable and filter by instanceof Entrypoint instead

1、webpack4.20 + ExtractTextWebpackPlugin，编译时报错：

Chunk.entrypoints: Use Chunks.groupsIterable and filter by instanceof Entrypoint instead

执行：yarn add extract-text-webpack-plugin@next

2、如果用到contenthash，会报另一个错：

Error: Path variable [contenthash] not implemented in this context: [name]_[contenthash].css

应该是版本问题，我的解决方法是，不使用contenthash，改用hash