Add a user activated webhook event to get notifications when users need to be approved manually

Hi,

For deployments where users need to be approved manually, there is no way to notify admins or moderators (via slack or email) that a user has verified his email address and is waiting for approval. Solving this would really help minimize user on-boarding time, to the benefit of themselves and the community.

I tried to send such a notification using zapier, following the topic below but then realized that a user verified event is missing from discourse: