docs: fix typo (#2899) [ci skip]

* Fix typo

* Adjust plurality since there is only one guide

Author: tdorsey

packages/@vue/cli-service/generator/template/src/components/HelloWorld.vue

@@ -3,7 +3,7 @@
   <div class="hello">
     <h1>{{ msg }}</h1>
     <p>
-      For guide and recipes on how to configure / customize this project,<br>
+      For a guide and recipes on how to configure / customize this project,<br>
       check out the
       <a href="https://cli.vuejs.org" target="_blank" rel="noopener">vue-cli documentation</a>.
     </p>