[Feature]: Guidance on archiving publications on EES

### Description

We should have guidance for how to archive publications on EES, covering 3 perspectives:

1. Publisher requesting this - information on what it is, why it's there and how to request it
2. EES admin implementing the change
3. General archiving policy for DfE stats and how that ties in

### Use case

As a publisher I want to know what the archiving of publications is, why and when I would use it, and how to request it.

### Why this is important

It's done very infrequently and currently isn't documented or clear. Having it written down will be helpful for us as knowledge leaves the team later in the year.

### Additional Context

There is a general guidance part that should exist, and then also create guidance around archiving publications on EES that says:

We will continue to use archiving to link publications when there has been a major change in the series leading to a new title, or multiple publications being combined into one.

- e.g. Apprenticeships and Traineeships > Apprenticeships

We will archive ad hocs that are superseded by / absorbed into regular publications and link them to the superseding publication.

- e.g. Free School Meals > SPC

Ad hocs and older publications with unique data not included elsewhere will remain visible. (there's a wider question on archiving these, but not one to worry about yet)