docs: improve theming dark mode section

docs/content/1.getting-started/3.theming.md

@@ -73,6 +73,48 @@ All the components are styled with dark mode in mind.
 
 Thanks to [Tailwind CSS dark mode](https://tailwindcss.com/docs/dark-mode#toggling-dark-mode-manually) class strategy and the [@nuxtjs/color-mode](https://github.com/nuxt-modules/color-mode) module, you literally have nothing to do.
 
+You can disable dark mode by setting the `preference` to `light` instead of `system` in your `nuxt.config.ts`.
+
+```ts [nuxt.config.ts]
+export default defineNuxtConfig({
+  colorMode: {
+    preference: 'light'
+  }
+})
+```
+
+::alert{icon="i-heroicons-light-bulb"}
+If you're stuck in dark mode even after changing this setting, you might need to remove the `nuxt-color-mode` entry from your browser's local storage.
+::
+
+You can easily build a dark mode switcher by using the `useColorMode` composable from `@nuxtjs/color-mode`.
+
+```vue
+<script setup>
+const colorMode = useColorMode()
+
+const isDark = computed({
+  get () {
+    return colorMode.value === 'dark'
+  },
+  set () {
+    colorMode.preference = colorMode.value === 'dark' ? 'light' : 'dark'
+  }
+})
+</script>
+
+<template>
+  <ClientOnly>
+    <UButton
+      :icon="isDark ? 'i-heroicons-moon' : 'i-heroicons-sun'"
+      color="gray"
+      variant="ghost"
+      @click="isDark = !isDark"
+    />
+  </ClientOnly>
+</template>
+```
+
 ## Components
 
 Components are styled with Tailwind CSS but classes are all defined in the default [app.config.ts](https://github.com/nuxtlabs/ui/blob/dev/src/runtime/app.config.ts) file. You can override them in your `app.config.ts`.