docs(readme) Use mini-css-extract-plugin in examples. (#568)

* update(readme) Use mini-css-extract-plugin in examples.

* update(readme) dont use variable for dev

README.md

@@ -18,7 +18,7 @@
   <p>Loads a Sass/SCSS file and compiles it to CSS.</p>
 </div>
 
-Use the [css-loader](https://github.com/webpack-contrib/css-loader) or the [raw-loader](https://github.com/webpack-contrib/raw-loader) to turn it into a JS module and the [ExtractTextPlugin](https://github.com/webpack-contrib/extract-text-webpack-plugin) to extract it into a separate file.
+Use the [css-loader](https://github.com/webpack-contrib/css-loader) or the [raw-loader](https://github.com/webpack-contrib/raw-loader) to turn it into a JS module and the [MiniCssExtractPlugin](https://github.com/webpack-contrib/mini-css-extract-plugin) to extract it into a separate file.
 Looking for the webpack 1 loader? Check out the [archive/webpack-1 branch](https://github.com/webpack-contrib/sass-loader/tree/archive/webpack-1).
 
 <h2 align="center">Install</h2>
@@ -45,13 +45,11 @@ module.exports = {
     module: {
         rules: [{
             test: /\.scss$/,
-            use: [{
-                loader: "style-loader" // creates style nodes from JS strings
-            }, {
-                loader: "css-loader" // translates CSS into CommonJS
-            }, {
-                loader: "sass-loader" // compiles Sass to CSS
-            }]
+            use: [
+                "style-loader", // creates style nodes from JS strings
+                "css-loader", // translates CSS into CommonJS
+                "sass-loader" // compiles Sass to CSS
+            ]
         }]
     }
 };
@@ -85,34 +83,31 @@ See [node-sass](https://github.com/andrew/node-sass) for all available Sass opti
 
 ### In production
 
-Usually, it's recommended to extract the style sheets into a dedicated file in production using the [ExtractTextPlugin](https://github.com/webpack-contrib/extract-text-webpack-plugin). This way your styles are not dependent on JavaScript:
+Usually, it's recommended to extract the style sheets into a dedicated file in production using the [MiniCssExtractPlugin](https://github.com/webpack-contrib/mini-css-extract-plugin). This way your styles are not dependent on JavaScript:
 
 ```js
-const ExtractTextPlugin = require("extract-text-webpack-plugin");
-
-const extractSass = new ExtractTextPlugin({
-    filename: "[name].[contenthash].css",
-    disable: process.env.NODE_ENV === "development"
-});
+const MiniCssExtractPlugin = require("mini-css-extract-plugin");
 
 module.exports = {
 	...
     module: {
         rules: [{
             test: /\.scss$/,
-            use: extractSass.extract({
-                use: [{
-                    loader: "css-loader"
-                }, {
-                    loader: "sass-loader"
-                }],
-                // use style-loader in development
-                fallback: "style-loader"
-            })
+            use: [
+                // fallback to style-loader in development
+                process.env.NODE_ENV !== 'production' ? 'style-loader' : MiniCssExtractPlugin.loader,
+                "css-loader",
+                "sass-loader"
+            ]
         }]
     },
     plugins: [
-        extractSass
+        new MiniCssExtractPlugin({
+            // Options similar to the same options in webpackOptions.output
+            // both options are optional
+            filename: "[name].css",
+            chunkFilename: "[id].css"
+        })
     ]
 };
 ```