title: vue3 isCustomElement is detecting component as a vue component
body: <p>I am trying to get a webcomponent working with vitejs.</p>
  <p>component I am trying to use:
  <a href="https://www.webcomponents.org/element/input-knob" rel="noreferrer">https://www.webcomponents.org/element/input-knob</a></p>
  <p>I did as describe in the docs.</p>
  <p>install and setup <code>@vitejs/plugin-vue</code></p>
  <p><a href="https://github.com/vitejs/vite/tree/main/packages/plugin-vue#vitejsplugin-vue-" rel="noreferrer">https://github.com/vitejs/vite/tree/main/packages/plugin-vue#vitejsplugin-vue-</a></p>
  <p>initiate the customelement in config. ( I also tried simply putting the custom element in main.js
  <a href="https://github.com/vitejs/vite/issues/1312" rel="noreferrer">https://github.com/vitejs/vite/issues/1312</a></p>
  <p>vite.config.js</p>
  <pre class="lang-js prettyprint-override"><code>
  import { VitePWA } from 'vite-plugin-pwa'
  import vue from '@vitejs/plugin-vue'
  export default {
    plugins: [
      VitePWA(),
      vue({
        template: {
          compilerOptions: {
            isCustomElement: tag =&gt; tag === 'input-knob'
          }
        }
      })
    ]
  }
  
  
  
  </code></pre>
  <p>still getting the same warning :frowning:</p>
  <pre class="lang-js prettyprint-override"><code>app.config.isCustomElement = tag =&gt; tag.startsWith('input-')
  
  console.log(app.config.isCustomElement('input-knob'))
  
  </code></pre>
  <p>main.js</p>
  <pre class="lang-js prettyprint-override"><code>
  import { createApp } from 'vue'
  import App from './App.vue'
  import './index.css'
  
  const app = createApp(App);
  
  app.config.isCustomElement = tag =&gt; tag.startsWith('input-')
  
  console.log(app.config.isCustomElement('input-knob'))
  app.mount('#app')
  
  
  </code></pre>
  <blockquote>
  <p>[Vue warn]: Failed to resolve component: input-knob</p>
  </blockquote>
  <p>the log returns true, so I am not sure where the problem actually is.</p>