The loose url regex does not support domains with more than 4 letter

[gianmarcocalbi]

The part of the loose url regex recognizing the domain is [a-z]{2,4} (https://github.com/Cretezy/linkify/blob/master/lib/src/url.dart#L10) while nowadays there are many domains name with more than 4 letters like .design, .travel, .cloud, etc.