@mentioning does not notify anyone

[MichaMican]

The @mentioning in gitbook currently is a little bit useless because there is no notification or listing of mentions for the mentioned user.
It would be great if

• There was an overview on which pages the signed in user is @mentioned.
• There was a notification (ideally via eMail) to the user that got @mentioned. It would propably also make sence to make this a user setting, where the user can opt out of these kind of notifications