Mark autoprefixer and cssnano as "production-only"

postcss.config.js

@@ -4,10 +4,12 @@ const cssnano = require('cssnano')
 module.exports = {
   plugins: [
     require('tailwindcss'),
-    require('autoprefixer'),
-    cssnano({
-      preset: 'default'
-    }),
+    process.env.NODE_ENV === 'production' ? require('autoprefixer') : null,
+    process.env.NODE_ENV === 'production'
+      ? cssnano({
+        preset: 'default'
+      })
+      : null,
     purgecss({
       content: ['./src/*.htm'],
       defaultExtractor: content => content.match(/[\w-/:]+(?<!:)/g) || []