Allow stage 3 css transforms (#5091)

* Switch to stage 3 css

* Tweak default browsers, too

Author: Timer

packages/react-dev-utils/browsersHelper.js

@@ -13,7 +13,12 @@ const inquirer = require('inquirer');
 const pkgUp = require('pkg-up');
 const fs = require('fs');
 
-const defaultBrowsers = ['>0.25%', 'not op_mini all', 'ie 11'];
+const defaultBrowsers = [
+  '>0.2%',
+  'not dead',
+  'not ie <= 11',
+  'not op_mini all',
+];
 
 function shouldSetBrowsers(isInteractive) {
   if (!isInteractive) {

packages/react-scripts/config/webpack.config.dev.js

@@ -60,7 +60,7 @@ const getStyleLoaders = (cssOptions, preProcessor) => {
             autoprefixer: {
               flexbox: 'no-2009',
             },
-            stage: 4,
+            stage: 3,
           }),
         ],
       },

packages/react-scripts/config/webpack.config.prod.js

@@ -72,7 +72,7 @@ const getStyleLoaders = (cssOptions, preProcessor) => {
             autoprefixer: {
               flexbox: 'no-2009',
             },
-            stage: 4,
+            stage: 3,
           }),
         ],
         sourceMap: shouldUseSourceMap,