docs: update color mode example

Author: atinux

Diff for: docs/content/3.examples/2.dark-mode.md

@@ -8,8 +8,32 @@ Live example of dark mode with Nuxt Tailwind on CodeSandbox.
 
 ---
 
-<!-- TODO: Replace with tailwind's native dark mode support. -->
-
 Example with the [tailwindcss-dark-mode](https://github.com/ChanceArthur/tailwindcss-dark-mode) plugin and [@nuxtjs/color-mode](https://github.com/nuxt-community/color-mode-module) module.
 
-:sandbox{src="https://codesandbox.io/embed/nuxt-dark-tailwindcss-17g2j"}
+To make it work hand-in-hand, you need to update your `tailwind.config` to add 
+
+```ts [tailwind.config.ts]
+import type { Config } from 'tailwindcss'
+
+export default <Partial<Config>>{
+  darkMode: 'class'
+}
+```
+
+And add the `classSuffix` to the colorMode module options:
+
+```ts [nuxt.config.ts]
+export default defineNuxtConfig({
+  modules: [
+    '@nuxtjs/tailwindcss',
+    '@nuxtjs/color-mode'
+  ],
+  colorMode: {
+    classSuffix: ''
+  }
+})
+```
+
+See the working demo below:
+
+:sandbox{src="https://stackblitz.com/edit/nuxt-tailwindcss-color-mode?embed=1&file=app.vue"}