I2P domains

[oooo-ps]

as understand, domain zone rule excludes digits - .onion works, but .i2p does not.
also ws://xxx.b32.i2p works but http://xxx.b32.i2p - does not.

fn valid_tld(tld: &str) -> bool {
    tld.chars()
        .take_while(|c| c.is_ascii_alphabetic())
        .take(2)
        .count()
        >= 2
}