Unable to use typescript 4 with react-scripts 4 and npm 7.0.5

Created by: MichaelHindley

One of the release notes for 4.0.0 is support for typescript v4, so as a user I'd expect to be able to use typescript 4 with react-scripts 4.0.0.

Case: package.json with react-scripts 4.0.0 and typescript 4.0.3 with npm on latest (7.0.5)