title: useState to update array of objects nested inside object
body: <p>I have state set as follows:</p>
  <pre><code>  const [groupState, setGroupState] = useState({
      groupId: uuidv4(),
      content: [],
    });
  </code></pre>
  <p>I want to push an object to the 'content' array but am having difficulty. I looked at this answer: <a href="https://stackoverflow.com/questions/55987953/how-do-i-update-states-onchange-in-an-array-of-object-in-react-hooks">How do I update states onchange in an array of object in React Hooks</a> but can't seem to apply it to the problem.</p>
  <p>Currently I have:</p>
  <pre><code>setGroupState({
    ...groupState,
    ...content.push({test: 'test'})
  });
  </code></pre>
  <p>.. but it's not working and I'm getting nowhere.</p>
  <p>Can anyone tell me how to get this sorted?</p>