Add support to time.Time

[cassioconti]

Hi, this is a request to extend the struct generation to support time fields. If the string matches the ISO 8601 / RFC 3339 patterns, like:

• 2021-07-28T12:34:56Z
• 2021-07-28T16:34:56-04:00

Then the type should time.Time instead of string. Thanks for the consideration.