fix(icon-button): add directive into button module (#13965)

Author: SisIvanova

projects/igniteui-angular/src/lib/directives/button/button.module.ts

@@ -1,12 +1,13 @@
 import { NgModule } from '@angular/core';
 import { IgxButtonDirective } from './button.directive';
+import { IgxIconButtonDirective } from './icon-button.directive';
 
 /**
  * @hidden
  * IMPORTANT: The following is NgModule exported for backwards-compatibility before standalone components
  */
 @NgModule({
-    imports: [IgxButtonDirective],
-    exports: [IgxButtonDirective]
+    imports: [IgxButtonDirective, IgxIconButtonDirective],
+    exports: [IgxButtonDirective, IgxIconButtonDirective]
 })
 export class IgxButtonModule {}