templates: reorders postcss plugins in the website template for tailwind compatibility (#10176)

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This The plugin order in postcss.config.js was causing UI rendering
issues in mobile Safari (#10135). This pull request affects the website
template and the vercel website template.

Current version:
```
// Website template:  /templates/website/postcss.config.js
// Vercel website template: /templates/with-vercel-website/postcss.config.js

export default {
  plugins: {
    autoprefixer: {},
    tailwindcss: {},
  },
}
```
PostCSS was loading Autoprefixer before Tailwind and the vendor prefixes
were not properly being prepended.

Fixed version (per [Tailwind
docs](https://tailwindcss.com/docs/browser-support)):

```
export default {
  plugins: {
    tailwindcss: {}, // this is first
    autoprefixer: {}, // this is second
  },
}
```

Author: gkennedy87

templates/website/postcss.config.js

@@ -1,6 +1,6 @@
 export default {
   plugins: {
-    autoprefixer: {},
     tailwindcss: {},
+    autoprefixer: {},
   },
 }

templates/with-vercel-website/postcss.config.js

@@ -1,6 +1,6 @@
 export default {
   plugins: {
-    autoprefixer: {},
     tailwindcss: {},
+    autoprefixer: {},
   },
 }