docs(reader): Document ReadUntil

Author: epage

src/reader.rs

@@ -4,7 +4,7 @@ use crate::error::Error;
 pub use regex::Regex;
 use std::io::prelude::*;
 use std::io::{self, BufReader};
-use std::sync::mpsc::{Receiver, channel};
+use std::sync::mpsc::{channel, Receiver};
 use std::thread;
 use std::{fmt, time};
 
@@ -206,6 +206,7 @@ impl NBReader {
     }
 }
 
+/// See [`NBReader::read_until`]
 pub enum ReadUntil {
     String(String),
     Regex(Regex),