Add a cli option to specify date type

[bryanjtc]

Description

I need to use the node api to make sure date-times are parsed as Dates and not strings.

Proposal

Create a simple cli flag: --date-time-type
Allow the values string or date

Extra

• I’m willing to open a PR (see CONTRIBUTING.md)

[duncanbeevers]

You can already accomplish this with the Node.js API and the transform option.
Because individual needs are likely to differ, it is unlikely this kind of functionality would be exposed as a command-line flag.

This library has no effect on how your data is parsed, so even if you're generating type Date for specific fields you'll need accompanying code to transform the JSON.parse results to something bespoke.