Add documentation about project removal

This adds documentation about how a user can remove a project, and
about how admins can view all projects pending removal. This feature
will soon be available for all users, so the admin aspect is not
important.

doc/user/project/index.md

@@ -173,6 +173,24 @@ Read through the documentation on [project settings](settings/index.md).
 - [Export a project from GitLab](settings/import_export.md#exporting-a-project-and-its-data)
 - [Importing and exporting projects between GitLab instances](settings/import_export.md)
 
+## Remove a project
+
+To remove a project, first navigate to the home page for that project.
+
+1. Navigate to **Settings > General**.
+1. Expand the **Advanced** section.
+1. Scroll down to the **Remove project** section.
+1. Click **Remove project**
+1. Confirm this action by typing in the expected text.
+
+### Delayed removal **(PREMIUM)**
+
+By default, clicking to remove a project is followed by a seven day delay. Admins can restore the project during this period of time.
+This delay [may be changed by an admin](../admin_area/settings/visibility_and_access_controls.md#default-deletion-adjourned-period-premium-only).
+
+Admins can view all projects pending deletion. If you're an administrator, go to the top navigation bar, click **Projects > Your projects**, and then select the **Removed projects** tab.
+From this tab an admin can restore any project.
+
 ## CI/CD for external repositories **(PREMIUM)**
 
 Instead of importing a repository directly to GitLab, you can connect your repository