support for default

[Licenser]

add #[serde(default)] as supported modifier

[ByteZ1337]

I'm currently implementing this here, and I was wondering how/if unnamed structs and enum variants should be handled? Given that deserialization currently only supports newtype unnamed structs, should the implementation only focus on named structs and panic when the attribute is used in other cases for the time being?
I'm also unsure what json would even need to be deserialized to reach a case where defaults for newtypes are needed.

[Licenser]

Heya first of all thank you for looking into this!

And yes, following the same model for unsupported types is totally fair :)