fix: color mode preference (#36)

components/DarkToggle.vue

@@ -1,7 +1,7 @@
 <script setup lang='ts'>
 const color = useColorMode()
 function toggleDark() {
-  color.preference = color.preference === 'dark' ? 'light' : 'dark'
+  color.preference = color.value === 'dark' ? 'light' : 'dark'
 }
 </script>