chore: fix PostCSS config example

Author: rigor789

README.md

@@ -68,7 +68,7 @@ In case you need to customize the postcss configuration, you can create a `postc
 
 module.exports = {
   plugins: [
-    tailwindcss: { config: "./tailwind.config.custom.js" },
+    ["tailwindcss", { config: "./tailwind.config.custom.js" }],
     "@nativescript/tailwind",
   ],
 };
@@ -166,4 +166,4 @@ Using the pre-built css is not recommended, since you lose the ability to config
   > **Note:** make sure you only include this once (for example in `App.vue`) - otherwise your bundle will contain the whole tailwind.css file multiple times.
 
 
-</details>
+</details>