fix: opacity level while data point selection

-feat: added the multiple selection without use of prolong mouse down event

Author: Adityakashyap1011

src/component/brush/BrushModel.ts

@@ -136,7 +136,7 @@ class BrushModel extends ComponentModel<BrushOption> {
     static defaultOption: BrushOption = {
         seriesIndex: 'all',
         brushType: 'rect',
-        brushMode: 'single',
+        brushMode: 'multiple',
         transformable: true,
         brushStyle: {
             borderWidth: 1,

src/component/toolbox/feature/Brush.ts

@@ -54,7 +54,7 @@ class BrushFeature extends ToolboxFeature<ToolboxBrushFeatureOption> {
 
         ecModel.eachComponent({mainType: 'brush'}, function (brushModel: BrushModel) {
             brushType = brushModel.brushType;
-            brushMode = brushModel.brushOption.brushMode || 'single';
+            brushMode = brushModel.brushOption.brushMode || 'multiple';
             isBrushed = isBrushed || !!brushModel.areas.length;
         });
         this._brushType = brushType;
@@ -120,9 +120,7 @@ class BrushFeature extends ToolboxFeature<ToolboxBrushFeatureOption> {
                     brushType: type === 'keep'
                         ? brushType
                         : (brushType === type ? false : type),
-                    brushMode: type === 'keep'
-                        ? (brushMode === 'multiple' ? 'single' : 'multiple')
-                        : brushMode
+                    brushMode: 'multiple'
                 }
             });
         }