fix(slider): focus the thumb when click over the track

Closes #5762

Author: Aleksandyr

projects/igniteui-angular/src/lib/slider/slider.component.ts

@@ -668,6 +668,7 @@ export class IgxSliderComponent implements
         activeThumb.nativeElement.setPointerCapture($event.pointerId);
         this.showSliderIndicators();
 
+        $event.preventDefault();
     }