expand and clarify field type

[pezra]

Expansion

There are a few more field types that would be widely useful. I suggest

• hidden - fields that must be in the submission but are immutable and provide no useful information to the user
• time - fields representing just the time of day
• datetime - fields have a date and time component
• text - fields that are expected to contain large amounts of text

Clarification

Make the fact that type is a hint more prominent and point out that clients should treat unrecognized types as string.

[pezra]

Would PRs be accepted? I'd be happy to draft these improvements if that would be helpful.

[jareddellitt]

Hey @pezra, sorry for the delayed response. Yes, PRs are welcome!