entry: {
    'module/a/index': 'module/a/index.js',
    'module/b/index': 'module/b/index.js',
},
output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js'
}

└── module
    ├── a
    │   └── index.js
    └── b
        └── index.js

from : https://stackoverflow.com/questions/35903246/how-to-create-multiple-output-paths-in-webpack-config