Support serde Deserialize and Serialize for Box<str, Allocator>

[JacksonUtsch]

Unable to use Box<T, A> in #[derive(Serialize, Deserialize)]

?Sized bound missing on Box fn serialize and fn deserialize

[zakarumych]

Please, specify on which type parameter you expect to have ?Sized bound.
If you mean T: Serialize + ?Sized then it's possible, but T: Deserialize + ?Sized is not, because Deserialize requires Sized.