docs: Add Email Notifications info (#9930)

* Add Email Notifications info

* remove spaces

* Add ` ` to smtp link

* Small fixes

* PR feedback

* npm run format:fix

* PR feedback

* update docs

* formatting

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Co-authored-by: Alex <alex.tran1502@gmail.com>

docs/docs/administration/email-notification.mdx

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+# Email Notifications
+
+Immich supports the option to send notifications via Email for the following events:
+
+- Creating a new user
+- Notifying a user when they get added to a shared album
+- Informing other users about the addition of new assets to a shared album
+
+## SMTP settings
+
+You can access the settings panel from the web at `Administration -> Settings -> Notification settings`
+
+Under Email, enter the following details to connect with SMTP servers.
+
+You can use the following [guide](/docs/guides/smtp-gmail) to use Gmail's SMTP server.
+
+<img src={require('./img/email-settings.png').default} width="80%" title="SMTP settings" />
+
+## User's notifications settings
+
+Users can manage their email notification settings from their account settings page on the web. They can choose to turn email notifications on or off for the following events:
+
+<img src={require('./img/user-notifications-settings.png').default} width="80%" title="User notification settings" />