fix(panel): keep the panel open when scrollbar is clicked #2091 (#2359)

Co-authored-by: Pavan Kumar Jadda <17564080+pavankjadda@users.noreply.github.com>

src/ng-select/lib/ng-dropdown-panel.component.ts

@@ -227,7 +227,7 @@ export class NgDropdownPanelComponent implements OnInit, OnChanges, OnDestroy {
         this._zone.runOutsideAngular(() => {
             merge(
                 fromEvent(this._document, 'touchstart', { capture: true }),
-                fromEvent(this._document, 'mousedown', { capture: true })
+                fromEvent(this._document, 'click', { capture: true })
             ).pipe(takeUntil(this._destroy$))
                 .subscribe($event => this._checkToClose($event));
         });