Appends a
\n character to each input string, then
concatenates the results. Equivalent to
foldMap (s ->
s ++ "\n").
>>> unlines ["Hello", "World", "!"]
"Hello\nWorld\n!\n"
Note that
unlines . lines /=
id when the input is not
\n-terminated:
>>> unlines . lines $ "foo\nbar"
"foo\nbar\n"