feat: add 404 page

layouts/error.vue

@@ -1 +1,12 @@
-<template>error!</template>
+<script setup lang="ts">
+import Default from "./default.vue";
+</script>
+
+<template>
+  <Default>
+    <main class="flex flex-col grow">
+      <h1>404 - Not Found</h1>
+      <p>The page you are looking for cannot be found.</p>
+    </main>
+  </Default>
+</template>