speed up json processing

[Sagleft]

Here is a speed comparison between the standard library and jsoniter:

Their interfaces are compatible, they perform the same role, but jsoniter is faster than the standard library. This is important because there is a lot of interaction built on the processing of json data from the exchange. Therefore, I propose to reduce the load on the CPU by simply replacing the library.

go test result:

0 0
1629771130463 1629771130463
PASS
ok      github.com/adshao/go-binance/v2 0.089s

[adshao]

@Sagleft great work, it's a huge performance improvement!