title: How to make a transparent modal with React Navigation 6 and expo
body: <p>I have just upgraded from React navigation 5 to 6 and looked at <a href="https://reactnavigation.org/docs/stack-navigator/#transparent-modals" rel="nofollow noreferrer">the doc for transparent modals</a>. Unfortunately, I cannot get the previous screen to show under the modal. Instead, I get a gray background.</p>
  <p>I have made a snack with my code to showcase my result: <a href="https://snack.expo.dev/@divone/transparent-modal-not-working" rel="nofollow noreferrer">https://snack.expo.dev/@divone/transparent-modal-not-working</a></p>
  <p>What am I doing wrong? I seem to have all the elements listed in the doc for it to work.</p>
  <p>I am on the managed workflow of expo SDK 43.</p>