Update doc - Email from GitLab

Needs refactor, besides update the images.

https://docs.gitlab.com/ee/tools/email.html

Changed title: EE - Email from GitLab → Update doc - Email from GitLab

Moved from gitlab-marketing/docs#3

Added gitlab-org/gitlab-ce~15078 label

Moved from gitlab-org/gitlab-ce#23162

changed milestone to %8.17

mentioned in issue gitlab-com/gitlab-docs#69 (closed)

changed milestone to %9.0

added docs-todo label

added docs-write and removed docs-todo labels

assigned to @marcia

Closing issue, will do when reworking Email topic index page.

closed