Remove use of global ApexCharts class

The `setupBrushHandler` method of the `Core` class relies on the
`ApexCharts` class' static `getChartByID` method. It calls this
static method on the `ApexCharts` class directly without
importing it currently.

This is fine if consuming `apexcharts` via
CDN / script tag as that places the exported `ApexCharts` class in
the global scope, but it becomes an issue when users want to
consume `apexcharts` via a package manager.

Update the `setupBrushHandler` method to call `ApexCharts.getChartByID`
the `Core` class' `ctx` field instead.

Author: SmithKy3

src/modules/Core.js

@@ -561,7 +561,7 @@ export default class Core {
   }
 
   setupBrushHandler() {
-    const { w } = this
+    const { ctx, w } = this
 
     if (!w.config.chart.brush.enabled) return
 
@@ -570,7 +570,7 @@ export default class Core {
         ? w.config.chart.brush.targets
         : [w.config.chart.brush.target]
       targets.forEach((target) => {
-        const targetChart = ApexCharts.getChartByID(target)
+        const targetChart = ctx.constructor.getChartByID(target)
         targetChart.w.globals.brushSource = this.ctx
 
         if (typeof targetChart.w.config.chart.events.zoomed !== 'function') {
@@ -585,7 +585,7 @@ export default class Core {
 
       w.config.chart.events.selection = (chart, e) => {
         targets.forEach((target) => {
-          const targetChart = ApexCharts.getChartByID(target)
+          const targetChart = ctx.constructor.getChartByID(target)
           targetChart.ctx.updateHelpers._updateOptions(
             {
               xaxis: {