[cli] make projectId and dataset optional for "sanity schema extract" command

[michael-land]

Is your feature request related to a problem? Please describe.
I want to generate types for a shared Sanity schema library.

Describe the solution you'd like
Exclude the checks for projectId and dataset.

Additional context
Are projectId and dataset necessary for schema extraction?

[sgulseth]

Thanks, agree that this should not be required for extracting the schema and generating types. We are not GA yet, but we'll put this in something to consider for that.