Supplemental documentation for the chomp method

Just a trivial doco change, but please let me know if I should put this into a branch prior to submitting a pull request.

```perl
$ printf "hello\nthere\n\nreader" | perl -MIO::All -E'$io = io("-")->chomp; while ( $line = $io->getline ) { print $line; } say;'
hellothere
$
```