No API for rates history

[g4s8]

It's not possible to access ZLD:USD or ZLD:BTC rates history, but WTS keeps it internally. Please add new API to get it, would be great if API user will be able to specify start date.

It may look like:
GET /rates?since=2019-01-01:

[
  {
    "usd_rate": "1.1",
    "timestamp": "2019-01-01T00:00:00.000Z"
  },

  {
    "usd_rate": "1.2",
    "timestamp": "2019-01-02T00:00:00.000Z"
  },

  {
    "usd_rate": "1.3",
    "timestamp": "2019-01-03T00:00:00.000Z"
  }
]

[0crat]

@yegor256/z please, pay attention to this issue