title: Merging object inside an interface in typescript
body: <p>I have the following in a typing file:</p>
  
  <pre><code>interface A {
      anObject: {
          data: string;
      };
      someOtherData: boolean;
  }
  </code></pre>
  
  <p>Now I want to change the interface so that <strong>anObject</strong> also includes <strong>data2</strong>. I want the final form to be</p>
  
  <pre><code>interface A {
      anObject: {
          data: string;
          data2: string;
      };
      someOtherData: boolean;
  }
  </code></pre>
  
  <p>I already tried doing this and it failed:</p>
  
  <pre><code>interface A {
      anObject: {
          data2: string;
      }
  }
  </code></pre>
  
  <p>Instead of the <strong>anObject</strong> having both data and data2, it only has data2. Is there anyway to keep original keys?</p>