fix(date-picker): export IDatePickerValidationFailedEventArgs

Author: MonikaKirkova

projects/igniteui-angular/src/lib/date-picker/public_api.ts

@@ -5,6 +5,7 @@ import { IgxPrefixDirective } from '../directives/prefix/prefix.directive';
 import { IgxSuffixDirective } from '../directives/suffix/suffix.directive';
 import { IgxDatePickerComponent } from './date-picker.component';
 
+export * from './date-picker.common';
 export * from './date-picker.component';
 
 /* NOTE: Date picker directives collection for ease-of-use import in standalone components scenario */