Running `juvix typecheck` outside of a juvix project should give a warning

[janmasrovira]

If you type juvix typecheck outside of a Juvix project, it will say "Well done! It type checks", because it typed checked the global project, but that can be confusing and it is most likely not what the user wants.
I believe there should be a message warning the user that you are not in a Juvix project. Maybe even an error.

[lukaszcz]

I would consider this an error. I can't a imagine a situation you would want this to typecheck the global project.