Yarn workspaces support

[Yzrsah]

It would be great if syncpack could work with yarn workspaces to help synchronize package versions across workspaces. A syncpack command specifying the root package.json could automatically use globs for workspaces.

[JamieMason]

Thanks @Yzrsah, there is similar support for Lerna so adding Yarn Workspaces support should hopefully be fairly approachable to you. The function that would need changing is getSources and its test suite is at /src/lib/get-packages.spec.ts, it is tested as an implementation detail of getPackages.

Your tests I think would need to mock out a package.json file which contains Yarn's workspaces property and assert that getPackages returns the expected package.json files.