title: check if interface has property?
body: <p>Need to check if interface has specific property. Tried/googled, but could not find appropriate solution.
  For example;</p>
  <pre><code>interface Props {
    id: string;
    name: string;
    age: number;
  }
  </code></pre>
  <p>What is best way to check if Props has &quot;age&quot; property?</p>