Request: Show Users who try to register with an existing email address a pop-up that it is already in use

[webmd-lsetch]

Presently, when a user tries to register with a previously registered email address, they continue into the email flow - where they are asked to reset their password.

We are interested in a pop-up message along the following lines:
That email address is attached to an existing user. Would you like to sign in?
Sign-In | Continue

Sign-In takes the user to the Sign In screen
Continue closes the pop-up and allows the user to update their email address etc.