add orderbook example using websocket

[2hyunbin]

I made an example of constructing an order book using WebSocket data(#265). The reviewer said that they would merge after refactoring the code(#242). I uploaded a new pr after refactoring the code, but it haven't checked it for weeks. I would appreciate it if you could check the PR.

[linear[bot]]

GH-73 add orderbook example using websocket