echarts 的柱状图颜色渐变

	series : [{
	                    name:'信息得分',
	                    type:'bar',
	                    barWidth: '20px',
	                    data:values,
	                    itemStyle: {
	                        normal: {
	                            color: new echarts.graphic.LinearGradient(0, 0, 0, 1, [
	                                {offset: 0, color: '#5a87c8'},
	                                {offset: 1, color: '#40ddce'}
	                            ])
	                        }
	                    },
	                }]