Perhaps add a refill method

[mgeisler]

It could be nice if textwrap supported "refilling" a paragraph. It should take an existing string like this

let help = "This is a long help text.
            It continues on this line
            since nicely-wrapped
            lines look better in the
            source code.

            This is a second paragraph
            in the same string.";

This string contains newlines and extra indentation. Refilling it would mean ignoring the extra newlines and indentation, and then otherwise wrapping it at some width.

Multiple paragraphs should probably be supported in order to make it extra convenient.