Make documentation its own section of the page
Make documentation its own section of the page

This visually chunks the page up into three parts:
- keys
- service ID
- documentation

Also fixes the documentation link (because it’s not service-specific).

gov-cjwaszczuk/notifications-admin,alphagov/notifications-admin,gov-cjwaszczuk/notifications-admin,gov-cjwaszczuk/notifications-admin,alphagov/notifications-admin,gov-cjwaszczuk/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin