Adding plugin postcss-flexbugs-fixes and flexbox: 'no-2009' to Autoprefixer (#1771)

* Adding postcss-flexbugs-fixes

Using postcss-flexbugs-fixes to fix all flexbug's issues.

* Adding flexbox: 'no-2009' to Autoprefixer

It will add flexbox prefixes only for final and IE versions of
specification.

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

@@ -197,6 +197,7 @@ module.exports = {
             options: {
               ident: 'postcss', // https://webpack.js.org/guides/migrating/#complex-options
               plugins: () => [
+                require('postcss-flexbugs-fixes'),
                 autoprefixer({
                   browsers: [
                     '>1%',
@@ -204,6 +205,7 @@ module.exports = {
                     'Firefox ESR',
                     'not ie < 9', // React doesn't support IE8 anyway
                   ],
+                  flexbox: 'no-2009',
                 }),
               ],
             },

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

@@ -202,6 +202,7 @@ module.exports = {
                   options: {
                     ident: 'postcss', // https://webpack.js.org/guides/migrating/#complex-options
                     plugins: () => [
+                      require('postcss-flexbugs-fixes'),
                       autoprefixer({
                         browsers: [
                           '>1%',
@@ -209,6 +210,7 @@ module.exports = {
                           'Firefox ESR',
                           'not ie < 9', // React doesn't support IE8 anyway
                         ],
+                        flexbox: 'no-2009',
                       }),
                     ],
                   },

packages/react-scripts/package.json

@@ -51,6 +51,7 @@
     "inquirer": "3.0.6",
     "jest": "19.0.2",
     "object-assign": "4.1.1",
+    "postcss-flexbugs-fixes": "2.1.0",
     "postcss-loader": "1.3.3",
     "promise": "7.1.1",
     "react-dev-utils": "^0.5.2",