Describe the bug

Navigating to the post editor in IE11 results in a blank page. Dev tools console shows multiple JS syntax errors.

To reproduce

Steps to reproduce the behavior:

1. Check out the master branch
2. On IE, in wp-admin, navigate to "new post" or any or edit any existing post.
3. Verify blank page results, open console and check errors (you may need to reload the page for all console errors to display)

Expected behavior

Post editor should work correctly in IE

Desktop (please complete the following information):

• OS: Windows 7, WIndows 10
• Browser: Internet Explorer
• Version: 11 (latest)

Additional context

There's a related issue in react-spring repo that outlines a solution: pmndrs/react-spring#552 (comment)
I have tested that fix on my local and it works; IE displays correctly after modifying webpack config and rebuilding.