Command to list projects in workspace

[spydon]

Now when the new workspaces feature is around the corner it would be great to have a command that listed the packages/apps in your workspace.

It could be something like this for example:

$ dart pub workspace-list
examples
flame
flame_tiled

And it would be good to have a flag that also gave the path of the projects, maybe in json or just some super simple text format?

$ dart pub workspace-list -v
examples: apps/examples/
flame: packages/flame
flame_tiled: packages/flame_tiled

This would be useful since then we don't have to duplicate that information in the melos config, or have to parse .dart_tool/package_config.json.