Support checkbox

[Munksgaard]

This is a tracking/discussion issue for supporting a checkbox style prompt. Such a prompt would allow the user to select more than one items from a list. The inspiration is the checkbox function from the Inquirer.js library:

This issue is for discussing such a feature and how to implement it.

[Munksgaard]

After reviewing the checkbox function from Inquirer.js, I think it feels overengineered.

• It functions as a sort of looping list, where you can scroll up and down infinitely.
• There is support for "headlines", disabled list items which just serve to categorize the items

To keep things simple, I think we should get rid of those two, and keep our library relatively simple.

However, I'm curious if anyone else thinks differently? Is there a need for categorization? Would you often have a list of 10+ choices (which might justify the loopy scrolling behavior)?

[Munksgaard]

I've started an implementation in #12.

Perhaps we need to support having some values enabled by default?