Support for #[serde(crate = "path")]

[tguichaoua]

I'm using rocket that exposes serde via the path rocket::serde.
To implement (de)serialize I'm using the attribute #[serde(crate = "rocket::serde")] to specifiy the path to serde.

[dtolnay]

I would prefer not to build this workaround into this crate.

Eventually rust-lang/rust#54363 (comment) will give a more robust way to make re-exported derive macros work without needing this kind of workaround.

In the meantime, it would be fine for someone else to maintain a more fully featured repr serde derive library that can handle this use case with an attribute.