OKX swap symbols

OKX perpetual swap instruments.

# Symbol Level Lot size Min order Tick size
501 ZRO-USDT-SWAP 20 1 1 0.0001
502 ZRX-USDT-SWAP 10 1 1 0.00001
503 XPD-USDT-SWAP 50 1 1 0.1
504 EWT-USDT-SWAP 20 0.01 0.01 0.01