Update slips.lua

Added new entries to slip 19:
lamb carving (3693)
polished lamb carving (3694)
Cait Sith carving (3695)
leafkin bopper (21097)
leafkin bopper +1 (21098)
Cait Sith cap (26717)
Cait Sith cap +1 (26718)
frosty cap (26728)