fix: wrong attributes added to next's forms

[Shywim]

Q	A
Branch?	main for features / current stable version branch for bug fixes
Tickets	#261
License	MIT
Doc PR

This fixes next generator not taking required, step and the correct type for the fields.

(I took some times to try having a clearer layout and use Formik's Field, but I did not see a nice a simple way to pass additional data to Field while being in the generator's loop, I thought it was better to leave this PR as simple as this 😅)

[dunglas]

Thank you!