Allow checkboxInput to accept values for checked and unchecked

[Pharserror]

Currently the checkboxInput type will set a value in the questionAnswers if the checkbox is checked. The goal of this issue would be to not set just one value but accept "checked" and "unchecked" values to set when the checkbox is checked or unchecked. For example, a checkbox for a boolean: the questionAnswers for an input named thing[foo] would be { thing: { foo: "true" } } for a checked checkbox and { thing: { foo: "false" } } for an unchecked checkbox.

More than happy to submit a PR. Give me the goahead 👍

Cheers,

• Pharse

[Pharserror]

Update: I need this for my own project now; so, I am working on this.