(Better?) Document the compatibility of version 1 and 2 serialized data

[shepmaster]

Congratulations on your release of version 2! 🎉

Reading through the release notes, I don't see an explicit statement about the compatibility of the serialized data between versions 1 and 2. I could see it going anywhere along the spectrum of (a) purely a Rust API change, no change to the serialization or (b) no Rust API changes at all but the serialization completely changes.

Perhaps this is documented in the migration guide? If so, I'd encourage you to link to this guide from the release notes.

Previously, I was using serialize_into / deserialize_from, which do not show up in the migration guide. I assume that they fall into the "No explicit Options, e.g. bincode::serialize(T)" part of the table, but I wonder if it would be worth having an exhaustive list of all such functions instead of letting the "e.g." be load-bearing.

The migration guide could benefit from being explicit about which kind of compatibility it means. Reading between the lines, I think it means of the serialized data, but spelling it out for us would be appreciated.

[VictorKoenders]

The specific line is If you want to be compatible with bincode 1, use the following table:; As long as you use the same config from bincode 1 and the related config in bincode 2, the serialized data is compatible.

Definitely could do with some better wording 👍