Add form displayMode

[remko-key]

Love the builder but Is it possible to add the new design modes when building the controllers:
https://docs.octobercms.com/3.x/extend/forms/form-controller.html#form-designs

The builders form display code looks a bit outdated to not using:

formRenderDesign() ?>

[daftspunk]

This is a great suggestion, thanks @remko-key !