Feat: Added spot & future testnet

[Prantadas7]

This PR includes: Future testnet support

• API: https://api.binance.com/api/v3/klines?
• WEBSOCKET: wss://stream.binance.com:9443/ws

Spot testnet support

• API: https://testnet.binance.vision/api/v3/klines?
• WEBSOCKET: wss://testnet.binance.vision/ws

Two additional(optional) props included:

• {Boolean} useFuturesTestnet
• {Boolean} useSpotTestnet