Add 404 page

src/components/404.vue

@@ -0,0 +1,12 @@
+<template>
+	<div class="content has-text-centered">
+		<h1>Not found</h1>
+		<p>The page you requested does not exist.</p>
+	</div>
+</template>
+
+<script>
+	export default {
+		name: '404'
+	}
+</script>