Attempt at disabling postcss-next warnings (#11518)

postcss.config.js

@@ -0,0 +1,18 @@
+/* globals module, require */
+module.exports = {
+  plugins: [
+    require('postcss-import'),
+    require('postcss-flexbugs-fixes'),
+    require('postcss-preset-env')({
+      autoprefixer: {
+        flexbox: 'no-2009',
+      },
+      stage: 3,
+      features: {
+        customProperties: {
+          warnings: false,
+        },
+      },
+    }),
+  ],
+};

postcssconfig.js

@@ -1,4 +0,0 @@
-/* globals module, require */
-module.exports = {
-  plugins: [require('autoprefixer')],
-};