Filter for Bypass or customize admin notification email after site creation

[dharmin16]

There is no functionality to bypass or update admin notification while site is created.
It will be helpful if anyone want to disable the admin notification of site creation.
I added the feature simmilar to wp_welcome_message().

E.g.

Filter 'wpmu_admin_notification' to disable or bypass.

Filter 'update_admin_notification' and 'update_admin_notification_subject'} to modify the content and subject line of the notification email.

[dharmin16]

Added the wpmu_admin_notification.

[afercia]

Thanks for the ticket and the patch, and welcome to Trac. To keep the ticket reports clean, I'm going to remove the accessibility focus, as this issue is not related to web content accessibility (a11y).

[dharmin16]

Duplicate of #42134.