Typed number in Rust with serde
support.
```rust use typednum::Num; use serdederive::{Serialize, Deserialize};
struct Config { version: Num<3>, hash: String, }
const OLD_CONFIG: &str = r#" version = 2 hash = "OoXQqX+ZRNE7VLmkbhGlj2R1B3n3gAJAaGh9kS0mAv8=" "#;
const NEW_CONFIG: &str = r#" version = 3 hash = "OoXQqX+ZRNE7VLmkbhGlj2R1B3n3gAJAaGh9kS0mAv8=" "#;
let newconfig = Config { version: Num, hash: "OoXQqX+ZRNE7VLmkbhGlj2R1B3n3gAJAaGh9kS0mAv8=".tostring(), };
toml::fromstr::