title: Property does not exist on the type in vue-class-component
body: <p>I got an error in my TypeScript component file that a prop doesn't exist, but I declared the prop exactly as described in the <a href="https://github.com/vuejs/vue-class-component#example" rel="noreferrer"><code>vue-class-component</code> documentation</a> example.</p>
  
  <pre><code>Property 'propMessage' does not exist on type 'MyComponent'.Vetur(2339)
  </code></pre>
  
  <p>How do I fix this?</p>
  
  <p><a href="https://i.stack.imgur.com/vr69o.png" rel="noreferrer"><img src="https://i.stack.imgur.com/vr69o.png" alt="screenshot of error"></a></p>