Consider adding Gong Zhu, a variant of Hearts in China

[iosonoungatto]

Hi dozingcat,

Thanks for making such a nice cat-based app. I was wondering whether it would be possible to add Gong Zhu (Pig), a variant of Hearts in China. The rules can be found here https://en.wikipedia.org/wiki/Gong_Zhu. The expose part can be skipped if it is too difficult to implement.