feat: introduce layouts (#28)

layouts/README.md

@@ -0,0 +1,13 @@
+## Layouts
+
+Vue components in this dir are used as layouts.
+
+By default, `default.vue` will be used unless an alternative is specified in the route meta.
+
+```html
+<script setup lang="ts">
+definePageMeta({
+  layout: 'home',
+})
+</script>
+```