ZB setLeverage
ZB setLeverage

Added setLeverage to ZB:
```
zb.setLeverage (5, BTC/USDT:USDT)
524 ms
{
  code: '10000',
  data: {
    createTime: '1644299964920',
    enableAutoAppend: '0',
    id: '6896693920064022533',
    keyMark: '6896693805014120448-100-',
    leverage: '5',
    marginCoins: 'USDT',
    marginCoinsIds: [ 6 ],
    marginCoinsNames: [ 'USDT' ],
    marginMode: '1',
    marketId: '100',
    maxAppendAmount: '0',
    modifyTime: '1645186271016',
    positionsMode: '2',
    userId: '6896693805014120448'
  },
  desc: '操作成功'
}
```

ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt