It's currently pretty complicated. We should turn this into a separate package with a build step, and probably use React as a dependency instead of vanilla JS code.

We shouldn't have the "duplicate React" issue because it's technically inside an iframe and would get its own copy of React. So if I understand it right, they wouldn't share any state, and if React in the app breaks, the one in the overlay should not be affected.

This should also work if the main app stops depending on React.