title: Possible to extend types in Typescript?
body: <p>Say I have the following type:</p>
  
  <pre><code>type Event = {
     name: string;
     dateCreated: string;
     type: string;
  }
  </code></pre>
  
  <p>I now want to extend this type, i.e.</p>
  
  <pre><code>type UserEvent extends Event = {
     UserId: string; 
  }
  </code></pre>
  
  <p>This doesn't work. How can I do this?</p>