Don't recommend to install '@types/foo' if that already exists

[ghost]

Fixes #24781

[DanielRosenwasser]

Almost there - I think it'd be helpful to say that if this resolved from an @types location, that we should elaborate with

If the '{0}' package actually exposes this module, consider sending a pull request to amend 'https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/{0}`