feanor-serde

This is a tiny library that provides some features to work with serde, in particular [serde::de::DeserializeSeed]s. I require these, since feanor-math and libraries building on it often need to serialize types that only exist as associated to some master object - e.g. ring elements, which belong to a ring. Hence, these can only be serialized and deserialized when given access to the master object, and thus must use [serde::de::DeserializeSeed]. Unfortunately, while serde makes it very convenient to implement [serde::Deserialize], not much utilities are provided for [serde::de::DeserializeSeed]. This library is a very small set of such utilities.