Assert a std::io::Read read_to_string() value is less than or equal to another.
Pseudocode:
(reader1.read_to_string(a) ⇒ a) ≤ (reader2.read_to_string(b) ⇒ b)
§Example
use std::io::Read;
let mut a = "alfa".as_bytes();
let mut b = "bravo".as_bytes();
assert_io_read_to_string_le!(a, b);
§Module macros