Bump postcard dependency to 1.0.0

[LightQuantum]

Postcard 1.0.0 fixed an issue which caused chrono types and #[serde_as(as = "DisplayFromStr")] failed to be serialized. See jamesmunns/postcard#32.

In my use case, I put http::Uri type into my identity type, which doesn't implement serde traits. So I used DisplayFromStr to work it around. However, postcard codec failed to serialize it due to the issue stated above.

[caio]

Thanks a lot for the report!

Would you like to submit a pull request for this? Otherwise I'll tentatively bump and release a new version this weekend

[caio]

I've just released v0.4.0 with your contribution. Closing the issue.

Thanks again!