Prioritise representative h-card parsing with expect=card

[barnabywalters]

XRay currently supports passing an expect: feed parameter when parsing, to skip content type detection and prioritise feed detection and parsing. It’s common for people to publish both a representative h-card and some sort of feed on their home page, and depending on exactly how they mark it up, XRay might return either a feed or card item. When the user knows that they want a representative h-card, it would be useful to be able to pass expect: card or similar to prioritise h-card parsing over feed parsing.

[aaronpk]

sounds reasonable to me!