make sure that tailwind has access to the AST

It's better to run this plugin first so Tailwind can operate on a single set of CSS after the imports have been inlined, like mentioned in the postcss-import documentation:
> This plugin should probably be used as the first plugin of your list. This way, other plugins will work on the AST as if there were only a single file to process, and will probably work as you can expect.
If you tried to @import any CSS file that was using Tailwind features like @responsive, this setup wouldn't work because Tailwind wouldn't see that code, it would only see an @import line. You want all of the imports inlined before running any other plugins.

examples/tailwindcss/postcss.config.js

@@ -1,7 +1,7 @@
 module.exports = {
   plugins: [
-    require('tailwindcss')('./tailwind.js'),
     require('postcss-import'),
+    require('tailwindcss')('./tailwind.js'),
     require('autoprefixer')
   ]
 }