Explain how to convert an anonymous volume to a named one

[Djaytan]

Typically, a trick is to rely on the --volume-from option from docker run command.

Let's experiment and then document that.

[Djaytan]

Relevant link: https://docs.docker.com/engine/storage/volumes/#remove-anonymous-volumes

[Djaytan]

Let's update the warning about data loss risk since to be fair I have the feeling it is removed anytime you remove the container in practice (e.g. deleting the container through Docker Desktop remove the associated anonymous volume too).

Overall, we can't really expect anonymous volumes to still live once its associated container does no longer exist.
We can just expect the anonymous to be useful in case someone want to export easily the data with --volume-from option.