feat: esModule option

Author: alexander-akait

README.md

@@ -118,6 +118,7 @@ module.exports = {
 |    **[`importLoaders`](#importloaders)**    |         `{Number}`          |   `0`    | Enables/Disables or setups number of loaders applied before CSS loader |
 | **[`localsConvention`](#localsconvention)** |         `{String}`          | `'asIs'` | Style of exported classnames                                           |
 |       **[`onlyLocals`](#onlylocals)**       |         `{Boolean}`         | `false`  | Export only locals                                                     |
+|         **[`esModule`](#esmodule)**         |         `{Boolean}`         | `false`  | Use ES modules syntax                                                  |
 
 ### `url`
 
@@ -857,6 +858,34 @@ module.exports = {
 };
 ```
 
+### `esModule`
+
+Type: `Boolean`
+Default: `false`
+
+By default, `css-loader` generates JS modules that use the CommonJS modules syntax.
+There are some cases in which using ES modules is beneficial, like in the case of [module concatenation](https://webpack.js.org/plugins/module-concatenation-plugin/) and [tree shaking](https://webpack.js.org/guides/tree-shaking/).
+
+You can enable a ES module syntax using:
+
+**webpack.config.js**
+
+```js
+module.exports = {
+  module: {
+    rules: [
+      {
+        test: /\.css$/i,
+        loader: 'css-loader',
+        options: {
+          esModule: true,
+        },
+      },
+    ],
+  },
+};
+```
+
 ## Examples
 
 ### Assets