chore(modal): expose global config interface (#5719)

src/modal/public_api.ts

@@ -2,7 +2,7 @@ export { BsModalRef } from './bs-modal-ref.service';
 export { ModalBackdropOptions } from './modal-backdrop.options';
 export { ModalContainerComponent } from './modal-container.component';
 export { ModalBackdropComponent } from './modal-backdrop.component';
-export { ModalOptions } from './modal-options.class';
+export { ModalOptions, MODAL_CONFIG_DEFAULT_OVERRIDE } from './modal-options.class';
 export { ModalDirective } from './modal.directive';
 export { ModalModule } from './modal.module';
 export { BsModalService } from './bs-modal.service';