Is it possible to use `normalizeEmail` with a custom domain

[sarincasm]

I have an app where most users are on a custom domain (the underlying account is google, so it follows the same rules). Can I use normalizeEmail to get a canonical version of such emails.

For Eg:
normalizeEmail('me+1@gmail.com') -> returns me@gmail.com

I want:
normalizeEmail('my+1@custom.com') -> should return my@custom.com

Maybe the custom domain that should be treated as same to a google email can be passed to normalizeEmail as an option

[saharme]

I added a PR with the change:
#1667