Possibly document how to transfer repositories between organisations

[himal-mandalia]

Document how to transfer repositories between organisations, based on this guide:

https://help.github.com/en/articles/transferring-a-repository#transferring-a-repository-owned-by-your-organization

We end up in a situation where repos are created external to the DfE Digital organisation, so would be good to have a concise guide to transfer repos over.

[happygeneralist]

Awareness of a central DFE repo for delivery managers is a good start. We weren't aware there was one until we started asking the question "what should we do with this?"

Steps I took:

1. If not already, request invitation to the DFE organisation
2. Check no sensitive information
3. Make repo public
4. Transfer ownership to DFE-digital (repo/settings/transfer)