Update webpack.config.js

fix indentation

Author: weilinzung

test/fixtures/success/webpack.config.js

@@ -1,7 +1,7 @@
 const FriendlyErrorsWebpackPlugin = require('../../../index');
 
 module.exports = {
-	mode: 'development',
+  mode: 'development',
   entry: __dirname + "/index.js",
   output: {
     path: __dirname + "/dist",