Docs feedback: No mention of new setting "Use unique domain" for pages

https://docs.gitlab.com/16.7/ee/user/project/pages/getting_started_part_one.html#urls-and-base-urls

There are no mentions about the new setting, and its potential impact, namely on baseurl.

@kassio : Strange that documentation was not in epic &9347 (closed)

Implementation Guide

Update https://docs.gitlab.com/16.7/ee/user/project/pages/getting_started_part_one.html#urls-and-base-urls to describe the new setting.