Fix bug: Tooltip not appearing for certain points (swimlane#501)

This fixes an issue where the tooltip would not appear for certain data
points. I had thirty data points in a line chart, and the tooltip was
not working for points 2-9. Looking further, I noticed that the array
of points along the x axis was not being sorted in the correct order.
The numbers were being sorted in alphabetical order (which explains why
10 came after 1), so I added a compare function in the related sorts to
sort the number in xSet numerically.

src/area-chart/area-chart-normalized.component.ts

@@ -334,7 +334,8 @@ export class AreaChartNormalizedComponent extends BaseChartComponent {
       const min = Math.min(...values);
       const max = Math.max(...values);
       domain = [min, max];
-      this.xSet = [...values].sort();
+      // Use compare function to sort numbers numerically
+      this.xSet = [...values].sort((a, b) => (a - b));
     } else {
       domain = values;
       this.xSet = values;

src/area-chart/area-chart-stacked.component.ts

@@ -318,7 +318,8 @@ export class AreaChartStackedComponent extends BaseChartComponent {
         : Math.max(...values);
 
       domain = [min, max];
-      this.xSet = [...values].sort();
+      // Use compare function to sort numbers numerically
+      this.xSet = [...values].sort((a, b) => (a - b));
     } else {
       domain = values;
       this.xSet = values;

src/area-chart/area-chart.component.ts

@@ -287,7 +287,8 @@ export class AreaChartComponent extends BaseChartComponent {
         : Math.max(...values);
 
       domain = [min, max];
-      this.xSet = [...values].sort();
+      // Use compare function to sort numbers numerically
+      this.xSet = [...values].sort((a, b) => (a - b));
     } else {
       domain = values;
       this.xSet = values;

src/line-chart/line-chart.component.ts

@@ -314,7 +314,8 @@ export class LineChartComponent extends BaseChartComponent {
         : Math.max(...values);
 
       domain = [min, max];
-      this.xSet = [...values].sort();
+      // Use compare function to sort numbers numerically
+      this.xSet = [...values].sort((a, b) => (a - b));
     } else {
       domain = values;
       this.xSet = values;