Modular page: form type is not allowed as content type.

Hi,

It sees that you can't manage this use case from the Admin UI: https://learn.getgrav.org/forms/forms/how-to-forms-in-modular-pages#using-forms-in-modular-pages

Indeed, when you want to add a modular page, you can't select "form" in the list. Meaning you can do it manually only.

It would be great if it could be done from the Admin :)

if the ``form`` blueprint should also be pasted in ``/blueprints//modular/``, it should be stated in the doc ;)

Thanks,
Nicolas