Docs are unclear on babel plugin vs webpack plugin

### Description

The https://github.com/gaearon/react-hot-loader#-hot-labs- section mentions that the webpack plugin is "required", but the getting started section doesn't include it.

### Expected behavior

It should be clear whether or not the webpack plugin is required

### Actual behavior

It's unclear whether it is required or not

### Environment

React Hot Loader version: 4.6.3

### Reproducible Demo

n/a