fix(combo): update styles of igx-combo-add-item (#15272)

Author: didimmova

projects/igniteui-angular/src/lib/combo/combo-add-item.component.ts

@@ -1,5 +1,5 @@
 import { IgxComboItemComponent } from './combo-item.component';
-import { Component } from '@angular/core';
+import { Component, HostBinding } from '@angular/core';
 
 /**
  * @hidden
@@ -8,9 +8,13 @@ import { Component } from '@angular/core';
     selector: 'igx-combo-add-item',
     template: '<ng-content></ng-content>',
     providers: [{ provide: IgxComboItemComponent, useExisting: IgxComboAddItemComponent }],
-    standalone: true
 })
 export class IgxComboAddItemComponent extends IgxComboItemComponent {
+    @HostBinding('class.igx-drop-down__item')
+    public get isDropDownItem(): boolean {
+        return false;
+    }
+
     public override get selected(): boolean {
         return false;
     }

projects/igniteui-angular/src/lib/core/styles/components/combo/_combo-theme.scss

@@ -209,7 +209,8 @@
     %igx-combo__add-item {
         height: auto !important;
         background: var-get($theme, 'empty-list-background') !important;
-        justify-content: center !important;
+        justify-content: center;
+        outline: none !important;
     }
 
     %igx-combo__empty {