add dark mode

src/components/mode-toggle.tsx

@@ -0,0 +1,40 @@
+'use client'
+
+import { Moon, Sun } from 'lucide-react'
+import { useTheme } from 'next-themes'
+import * as React from 'react'
+
+import { Button } from '@/components/ui/button'
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu'
+
+export function ModeToggle() {
+  const { setTheme } = useTheme()
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button variant='outline' size='icon'>
+          <Sun className='dark:-rotate-90 h-[1.2rem] w-[1.2rem] rotate-0 scale-100 transition-all dark:scale-0' />
+          <Moon className='absolute h-[1.2rem] w-[1.2rem] rotate-90 scale-0 transition-all dark:rotate-0 dark:scale-100' />
+          <span className='sr-only'>Toggle theme</span>
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align='end'>
+        <DropdownMenuItem onClick={() => setTheme('light')}>
+          Light
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme('dark')}>
+          Dark
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme('system')}>
+          System
+        </DropdownMenuItem>
+      </DropdownMenuContent>
+    </DropdownMenu>
+  )
+}