SELECT lead_envoy FROM table_name_10 WHERE ryūkyūan_king = "shō kei" AND mission_type = "congratulation" AND year = 1718
Who was the lead envoy of the congratulation mission in 1718 with the Ry ky an King sh kei?
CREATE TABLE table_name_10 (
    lead_envoy VARCHAR,
    year VARCHAR,
    ryūkyūan_king VARCHAR,
    mission_type VARCHAR
)