Can I change `yaml` for `toml` because yaml [not implement zero copy deserializer]( https://github.com/dtolnay/serde-yaml/blob/master/src/de.rs#L1007), while [toml does implement it](https://github.com/alexcrichton/toml-rs/blob/master/src/de.rs#L75-L83)? I need it because I'm fixing the copy at `Snippet` to `DisplayList` cast