Better EDUPLICATEWORKSPACE output

[midudev]

When working with huge monorepo multipackage with workspaces, sometimes you could find you're using the same package name twitch without noticing.

While trying to install packages it throws an error:
$ npm install
npm ERR! code EDUPLICATEWORKSPACE
npm ERR! must not have multiple workspaces with the same name

It would be nice if the error tells you exactly which packages have the same name. Specially useful on CI environments.