Coinex createReduceOnlyOrder
Coinex createReduceOnlyOrder

Added createReduceOnlyOrder method to Coinex:
```
node examples/js/cli coinex createReduceOnlyOrde
r BTC/USDT:USDT limit sell 0.0005 40000 '{"positionId":"67832325"}'

coinex.createReduceOnlyOrder (BTC/USDT:USDT, limit, sell, 0.0005, 40000, [object Object])
2022-05-03T01:17:02.320Z iteration 0 passed in 308 ms

{
  id: '18992417473',
  clientOrderId: undefined,
  datetime: '2022-05-03T01:17:01.913Z',
  timestamp: 1651540621913,
  lastTradeTimestamp: 1651540621913,
  status: undefined,
  symbol: 'BTC/USDT:USDT',
  type: 'limit',
  timeInForce: undefined,
  postOnly: undefined,
  side: 'sell',
  price: 40000,
  stopPrice: undefined,
  cost: 0,
  average: undefined,
  amount: 0.0005,
  filled: 0,
  remaining: 0.0005,
  trades: [],
  fee: { currency: '', cost: 0 },
  info: {
    amount: '0.0005',
    client_id: '',
    create_time: '1651540621.913061',
    deal_asset_fee: '0.00000000000000000000',
    deal_fee: '0.00000000000000000000',
    deal_profit: '0.00000000000000000000',
    deal_stock: '0.00000000000000000000',
    effect_type: '1',
    fee_asset: '',
    fee_discount: '0.00000000000000000000',
    last_deal_amount: '0.00000000000000000000',
    last_deal_id: '0',
    last_deal_price: '0.00000000000000000000',
    last_deal_role: '0',
    last_deal_time: '0',
    last_deal_type: '0',
    left: '0.0005',
    leverage: '3',
    maker_fee: '0.00030',
    market: 'BTCUSDT',
    order_id: '18992417473',
    position_id: '0',
    position_type: '1',
    price: '40000.00',
    side: '1',
    source: 'api.v1',
    stop_id: '0',
    taker_fee: '0.00050',
    target: '0',
    type: '1',
    update_time: '1651540621.913061',
    user_id: '3620173'
  },
  fees: [ { currency: '', cost: 0 } ]
}
```

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