Feature: regex for AUTOCONFIRM

Already posted as netlify/gotrue#331

Right now, it is possible to set AUTOCONFIRM to true or false for email and phone.
Sometimes, it could be needed to autoconfirm emails from specific domains, or phone numbers from specific countries.

A workaround is possible by setting the status of the created account elsewhere than in gotrue, but the confirmation email would still be sent.

I think it could be useful to provide optional regexes through configuration, and, if the registering email address / phone number matches, it would autoconfirm.

Thanks in advance for considering this issue, whether or not it falls in the scope of this project