Issue parsing Riichi City log

[peter1357908]

Riichi city logs can have a seat-indicator suffix after the 20-char string:

cu8hpmpbimvtg7crj7fg@2

However, /skill only allows the 20-char string at the moment.

Also, the description of the command needs to be updated (to say support for Riichi City).

Finally, feeding the 20-char string without @2 still resulted in a bug.