Undocumented property `value_type` in Array field

[aricooperdavis]

The Array field introduced in the Form plugin has an undocumented property value_type which can be set to value_type: textarea to change the value entry element from an <input> to a <textarea>.

This is useful, but undocumented.

Shall I document this, or is there a reason why it's not in the docs at the moment?

[rhukster]

Please document it :)

It's very hard for me to keep the code and docs in sync by myself so any help is appreciated.