question: Who was the lead envoy of the congratulation mission in 1718 with the Ryūkyūan King shō kei?
answer: SELECT lead_envoy FROM table_name_10 WHERE ryūkyūan_king = "shō kei" AND mission_type = "congratulation" AND year = 1718
context: CREATE TABLE table_name_10 (lead_envoy VARCHAR, year VARCHAR, ryūkyūan_king VARCHAR, mission_type VARCHAR)