Digifinex fetchBorrowRate, fetchBorrowRates
Digifinex fetchBorrowRate, fetchBorrowRates

Added fetchBorrowRate and fetchBorrowRates to Digifinex:

fetchBorrowRate:
```
digifinex.fetchBorrowRate (BTC)
2022-06-07T20:01:31.345Z iteration 0 passed in 1370 ms

{
  currency: 'BTC',
  rate: 0.001,
  period: 86400000,
  timestamp: 1654632091345,
  datetime: '2022-06-07T20:01:31.345Z',
  info: {
    valuation_rate: '1',
    total: '0.0013930827',
    free: '0.0013930827',
    currency: 'BTC'
  }
}
```

fetchBorrowRates:
```
digifinex.fetchBorrowRates ()
2022-06-07T20:01:13.180Z iteration 0 passed in 1419 ms

{
  USDT: {
    currency: 'USDT',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: {
      valuation_rate: '1',
      total: '1.92012186174',
      free: '1.92012186174',
      currency: 'USDT'
    }
  },
  BTC: {
    currency: 'BTC',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: {
      valuation_rate: '1',
      total: '0.0013930827',
      free: '0.0013930827',
      currency: 'BTC'
    }
  },
  ETH: {
    currency: 'ETH',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'ETH' }
  },
  LTC: {
    currency: 'LTC',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'LTC' }
  },
  XRP: {
    currency: 'XRP',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'XRP' }
  },
  EOS: {
    currency: 'EOS',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'EOS' }
  },
  BCH: {
    currency: 'BCH',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'BCH' }
  },
  BSV: {
    currency: 'BSV',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'BSV' }
  },
  ETC: {
    currency: 'ETC',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'ETC' }
  },
  DFT: {
    currency: 'DFT',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '0.7', total: '0', free: '0', currency: 'DFT' }
  },
  DRV: {
    currency: 'DRV',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'DRV' }
  },
  DASH: {
    currency: 'DASH',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'DASH' }
  },
  QTUM: {
    currency: 'QTUM',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'QTUM' }
  },
  NEO: {
    currency: 'NEO',
    rate: 0.001,
    period: 86400000,
    timestamp: 1654632073180,
    datetime: '2022-06-07T20:01:13.180Z',
    info: { valuation_rate: '1', total: '0', free: '0', currency: 'NEO' }
  }
}
```

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