How to create custom block with new version?

In previous versions, I used the following example format to create a custom block:
```js
const eslint = () => () => ({
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: ['eslint-loader']
      }
    ],
  },
})
```

How to create a custom block with new webpack blocks version?