title: Preview content on site in Sanity not working
body: <p>I'm following the Sanity docs on how to add a <a href="https://www.sanity.io/docs/preview-content-on-site" rel="nofollow noreferrer">content preview</a>. After updating the <code>sanity.json</code> and adding a <code>resolveProductionUrl.js</code> file according to docs I should be able to see a menu item in context menu:</p>
  <p><a href="https://i.stack.imgur.com/2jlid.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2jlid.png" alt="enter image description here" /></a></p>
  <p>But it's not happening. Interestingly enough If I add a console log to a <code>resolveProductionUrl.js</code> I can see it on the browser console - meaning that this function is getting called.</p>
  <p>This is what I see:</p>
  <p><a href="https://i.stack.imgur.com/zJhnY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zJhnY.png" alt="enter image description here" /></a></p>