Add documentation for switch thumb slot

apps/www/src/content/docs/components/switch.md

@@ -48,6 +48,19 @@ import { Switch } from '@/components/ui/switch'
 </template>
 ```
 
+# Add icon inside switch thumb
+
+```vue
+<template>
+  <Switch :checked="isDark" @update:checked="toggleTheme">
+      <template #thumb>
+          <Icon v-if="isDark" icon="lucide:moon" class="size-3"></Icon>
+          <Icon v-else icon="lucide:sun" class="size-3"></Icon>
+      </template>
+  </Switch>
+</template>
+```
+
 ## Examples
 
 ### Form