Module not found: Error: Can’t resolve ‘react-dom/client’ in 'node_modules/evergreen-ui/esm/toaster/src’

Some internal users have reported a warning from the dynamic import of `react-dom/client` in the Toaster component that was added in #1494. It seems to still "work", but I'm not super familiar with esm - perhaps we should roll this change back and deal with the original `ReactDOM.render` warning.