Get real-time order book bids and asks.
/v1/market/depth
BTCUSDT, ETHUSDT, ADAUSDT
US Stocks: AAPL.US, TSLA.US, MSFT.US
HK Stocks: 700.HK, 9988.HK, 3690.HK
Trading symbol
"BTCUSDT"
Depth levels (default 10, max 50)
1 <= x <= 5020