Revert "remove autoprefixer"

This reverts commit 00b6a2e.

Author: forsartis

README.md

@@ -24,6 +24,7 @@ module.exports = {
   plugins: {
     tailwindcss: {},
     'vue-cli-plugin-tailwind/purgecss': {},
+    autoprefixer: {},
   },
 };
 ```
@@ -56,6 +57,7 @@ module.exports = {
     'vue-cli-plugin-tailwind/purgecss': {
       whitelist: ['foo', 'bar'],
     },
+    autoprefixer: {},
   },
 };
 ```