Step Lineecharts 折线配置项内容和展示

官网用例， 高度图测试

      option = {
    xAxis: {
        type: 'category',
        boundaryGap: false,
        data: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
    },
    yAxis: {
        type: 'value'
    },
    series: [{
        data: [820, 932, 901, 934, 1290, 1330, 1320],
        type: 'line',
        step: 'end',
        areaStyle: {}
    },{
        data: ['-', '-', '-', 934, 1290, 1330, '-'],
        type: 'line',
        step: 'end',
        areaStyle: {}
    }]
};