Add support for in-memory NutsDB

[zx8]

Since v0.7.0, NutsDB has supported in-memory storage.

Looking through the configuration parsing code for NutsDB for Caddy, it seems that Souin does not yet support an in-memory option.

Is this an option you might consider adding?

Thank you!

[darkweak]

Hello, @zx8 thank you for pointing out this feature. We will be able to replace badger default storage by nutsdb in memory with that! 👍