Hi,

Though it is not necessarily a bug[1], Firefox renders this as
a link but shr doesn't:

<span href="https://www.example.com" style="font-size:...">Foo</span>

Jidanni wrote me that some html mails he receives contain such
forms, and I tried making shr support it as the patch attached
below.  I'm not quite sure whether it causes a trouble but I'm
going to try it for some time.

Thanks.

[1] <https://stackoverflow.com/questions/46889226/is-a-span-tag-with-a-href-attribute-considered-valid>