Add Font Family Feature to CKEditor Toolbar in Angular

Sadly I could not manage to add the font family feature to the CKEditor's toolbar in Angular.

I'm getting the following error in the console:

toolbarview-item-unavailable: The requested toolbar item is unavailable. Read more: https://ckeditor.com/docs/ckeditor5/latest/framework/guides/support/error-codes.html#error-toolbarview-item-unavailable

{name: "fontFamily"}

Here is how my project looks like:

app.module.ts

...
import { CKEditorModule } from '@ckeditor/ckeditor5-angular';
import { CkeditorComponent } from './ckeditor/ckeditor.component';
...

@NgModule( {
    declarations: [
        ...
        CkeditorComponent
    ],
    imports: [
        ...
        CKEditorModule,
        ...
    ],
    ...
} )

ckeditor.component.ts

import * as BalloonEditor from '@ckeditor/ckeditor5-build-balloon';

@Component( {
    ...
} )

export class CkeditorComponent {
    public Editor = BalloonEditor;

    public editorConfig = {
        fontFamily: {
          options: [
            'default',
            'Ubuntu, Arial, sans-serif',
            'Ubuntu Mono, Courier New, Courier, monospace'
          ]
        },
        toolbar: [
          'heading', 'bulletedList', 'numberedList', 'fontFamily'
        ]
    };
}

ckeditor.component.html

<ckeditor 
  [editor]="Editor" 
  [config]="editorConfig"
  data="<p>Hello world!</p>"></ckeditor>