Component legend.scroll not exists. Load it first.

echarts在项目中用的按需加载，在配置legend.type = 'scroll'后报错：

 之前已经引入legend组件了，require('echarts/lib/component/legend');

后来在官网找到 legendScroll 需要单独引入。

以下是所有按需引入列表：

let echarts = require('echarts/lib/echarts');

require("echarts/lib/component/dataset");

require("echarts/lib/chart/line");

require("echarts/lib/chart/bar");

require("echarts/lib/chart/pie");

require("echarts/lib/chart/scatter");

require("echarts/lib/chart/radar");

require("echarts/lib/chart/map");

require("echarts/lib/chart/tree");

require("echarts/lib/chart/treemap");

require("echarts/lib/chart/graph");

require("echarts/lib/chart/gauge");

require("echarts/lib/chart/funnel");

require("echarts/lib/chart/parallel");

require("echarts/lib/chart/sankey");

require("echarts/lib/chart/boxplot");

require("echarts/lib/chart/candlestick");

require("echarts/lib/chart/effectScatter");

require("echarts/lib/chart/lines");

require("echarts/lib/chart/heatmap");

require("echarts/lib/chart/pictorialBar");

require("echarts/lib/chart/themeRiver");

require("echarts/lib/chart/sunburst");

require("echarts/lib/chart/custom");

require("echarts/lib/component/grid");

require("echarts/lib/component/polar");

require("echarts/lib/component/geo");

require("echarts/lib/component/singleAxis");

require("echarts/lib/component/parallel");

require("echarts/lib/component/calendar");

require("echarts/lib/component/graphic");

require("echarts/lib/component/toolbox");

require("echarts/lib/component/tooltip");

require("echarts/lib/component/axisPointer");

require("echarts/lib/component/brush");

require("echarts/lib/component/title");

require("echarts/lib/component/timeline");

require("echarts/lib/component/markPoint");

require("echarts/lib/component/markLine");

require("echarts/lib/component/markArea");

require("echarts/lib/component/legendScroll");

require("echarts/lib/component/legend");

require("echarts/lib/component/dataZoom");

require("echarts/lib/component/dataZoomInside");

require("echarts/lib/component/dataZoomSlider");

require("echarts/lib/component/visualMap");

require("echarts/lib/component/visualMapContinuous");

require("echarts/lib/component/visualMapPiecewise");

require("echarts/zrender/lib/vml/vml");

require("echarts/zrender/lib/svg/svg");