inttype-enum

Converts an [enum] into an [inttype], and try to convert it back

Usage example:
```rs

[derive(IntType)]

[repr(u8)]

enum Cmd { Connect = 1, Bind = 2, Udp = 3, }

let conn: u8 = Cmd::Connect.into(); assert!(matches!(Cmd::tryfrom(conn), Ok(Cmd::Connect))); assert!(matches!(Cmd::tryfrom(0), Err(_))); ```