Expand description
Derive macro for #[derive(Encodable, Decodable)].
For example of usage see ./tests/rlp.rs.
This library also supports up to 1 #[rlp(default)] in a struct,
which is similar to #[serde(default)]
with the caveat that we use the Default value if
the field deserialization fails, as we don’t serialize field
names and there is no way to tell if it is present or not.