Reset cached orderbook when new orderbook is a snapshot

[v36u]

This idea came while looking over Bybit's API:

Once you have subscribed successfully, you will receive a snapshot. The WebSocket will keep pushing delta messages every time the orderbook changes. If you receive a new snapshot message, you will have to reset your local orderbook. If there is a problem on Bybit's end, a snapshot will be re-sent, which is guaranteed to contain the latest data.

https://bybit-exchange.github.io/docs/v5/websocket/public/orderbook#process-snapshotdelta

It seems like common sense to reset the old orderbook when the new one is a full one. Also, the impact would be very reduced because the only ones that set IsFromSnapshot to true are Bybit and KuCoin.

I've also updated the readme to reflect that Bybit and KuCoin have orderbook websockets implemented.