Extend list command to show required vars, maybe via --list --verbose

[solvingj]

Description

Required vars is an epic quality-of-life feature. Thank you to all. If task -lv also printed "required" vars, it would make UX around discovery and understanding of task operations in new projects much better. Seems very straightforward aside from the alignment cosmetics.

The "problem" I see is that it could open the door to more feature requests like "required var descriptions", "declare optionals just like required", etc. Basically, people trying to take things ever further to the eventual point of full blown arg processing like flag/cobra/argparse/etc. I don't know if that hypothetical should preclude implementing this simple improvement, but I did think of it.

[pd93]

@solvingj Thanks for the suggestion. I've added this to the List Experiment parent issue. We can consider something around required vars in that proposal.