Bump version to v0.11.0

This _shouldn't_ be a breaking change because `Visitor::visit_string`
has a default implementation[^1] which simply forwards to
`Visitor::visit_str`. So any visitors that currently expect to receive
strings via `visit_str` should continue to get them. AFAIK the only way
that won't happen is if they explicitly implement `visit_string` and
fail. That seems unrealistic but I'll bump the minor version here just
in case.

Actually, now that we're bumping the MSRV in this PR we should probably
bump the minor version anyway.

[^1]: https://github.com/serde-rs/serde/blob/d17902059e77e371d8a7f83ff403f9e760b70f45/serde_core/src/de/mod.rs#L1568-L1573

Author: cstyles

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_magnus"
-version = "0.10.0"
+version = "0.11.0"
 description = "Serde integration for Magnus"
 edition = "2018"
 rust-version = "1.68"