updated book's forms

src/app/components/create-book/create-book.ts

@@ -1,17 +1,17 @@
 import { Component } from '@angular/core';
 import {NzFormModule} from "ng-zorro-antd/form";
 import {FormControl, FormGroup, ReactiveFormsModule, Validators} from "@angular/forms";
-import {NzFlexDirective} from "ng-zorro-antd/flex";
 
 @Component({
   selector: 'app-create-book',
-    imports: [NzFormModule, NzFlexDirective, ReactiveFormsModule],
+    imports: [NzFormModule, ReactiveFormsModule],
   templateUrl: './create-book.html',
   styleUrls: ['./create-book.css'],
 })
 export class CreateBook {
     createBookForm = new FormGroup({
         title: new FormControl<string>(null, [Validators.required]),
+        isbn: new FormControl<string>(null, [Validators.required]),
         releaseYear: new FormControl<string>(null, [Validators.required]),
         author: new FormControl<string>(null, [Validators.required])
     })