JSON: add jsoniter lib to json benchmark

[euskadi31]

see: https://github.com/json-iterator/go

	ns/op	allocation bytes	allocation times
std decode	35510 ns/op	1960 B/op	99 allocs/op
easyjson decode	8499 ns/op	160 B/op	4 allocs/op
jsoniter decode	5623 ns/op	160 B/op	3 allocs/op
std encode	2213 ns/op	712 B/op	5 allocs/op
easyjson encode	883 ns/op	576 B/op	3 allocs/op
jsoniter encode	837 ns/op	384 B/op	4 allocs/op