Username normalization

Hi Jonathan,

First of all thanks a lot for the contrib with this plugin.

We noticed that before creating a user you remove special characters (such as @):
https://ibb.co/kngsaA

We would like usernames to be emails, including the @ character.
Typically username = ‘[email protected]’

Do you think it would make sense to have the possibility to turn on/off the normalize action using a toggle button in the config ? So that I could for example decide to leave special characters.

We initially wanted to fork your project to implement this, but thought it would make more sense to contribute instead.

Thanks in advance for your answer,
Laurent.