E501: strings links should allow “introduction”

[xZise]

The line length checker excepts URL only lines because of #224 which is sensible. But usually there is some introduction like:

So maybe there is a way to allow something before an URL when it's a comment or doc string. The question is now what is sensible. Maybe something like [^ ]+: so it would allow the above line or something like:

See: https://example.com/a-very-very-very…

It wouldn't allow “See also:” so maybe it should just strip the URL and check the rest of the line?