fix(linky): make urls starting with www. into links

The filter was not turning urls like starting with `www.` (like `www.example.com`) into links. These changes address that.
@caitp: Your 1st suggestion alters the "meaning" of the RegExp, so won't work correctly.
In the 2nd comment, you probably mean `match[3]` (and should indeed work) :smiley: