Show "soft" email requirement instructions

[q-wertz]

Steps to reproduce

Start registration

Expected behaviour

Additionally to the already existing User instructions, it would be nice to have one, that is shown when the user enters his/her email address. This way, one could add "soft" requirements to the emails.

Actual behaviour

Currently this could be added to the Registration form instructions not sure when this is shown or the Verification email instructions which is too late to specify the email requirements

Server configuration

Nextcloud version: 28.0.4
Registration app version: 2.4.0