Encoder interface not respected for `interface{}` types

[TomK]

when encoding a struct field with an interface{} or any type, using a type that implements Encoder is not respected

It seems that only the field type in the struct is checked for Encoder interface, and not the value of the field.

Playground: https://go.dev/play/p/VTG-X_HgunK

[TomK]

@willnorris are you accepting PRs for this project? Is there any point in me investing time looking into this?

[willnorris]

I'm not actively using or working on the project anymore, so have been pretty resistant to adding new features. But something like this should likely be pretty small, so I think would be fine.