Improve hint about private Email in invite
Improve hint about private Email in invite

Whenever a user has set his Email in GitHub to private,
this user can't be invited without providing an Email address.
This is now explained more clearly.
RayRutjes/frontend,RayRutjes/frontend,circleci/frontend,prathamesh-sonpatki/frontend,circleci/frontend,prathamesh-sonpatki/frontend,circleci/frontend