feat; add multi language support

src/app/pages/main/main.html

@@ -1,13 +1,13 @@
-<app-main-header [title]="strings.contactList"/>
+<app-main-header [title]="languageManager.strings.contactAgenda"/>
 <app-card bgColor="var(--secondary)">
     <app-contact-form 
         (contact)="save($event)"
         [form]="form"
-        [submitText]="strings.add"
+        [submitText]="languageManager.strings.add"
         class="form" 
     ><app-form-header 
-            [subtitle]="strings.allFieldRequired|upperfirst"
-            [title]="strings.addContact|upperfirst" 
+            [subtitle]="languageManager.strings.allFieldRequired|upperfirst"
+            [title]="languageManager.strings.addContact|upperfirst" 
             slot="header"
         />
     </app-contact-form>

src/app/pages/main/main.ts

@@ -5,10 +5,10 @@ import { ContactList } from '../../components/contact-list/contact-list';
 import { ContactService } from '../../services/contact.service';
 import { ContactDTO } from '../../models/ContactDTO';
 import { FormHeader } from '../../components/form-header/form-header';
-import { STRINGS_INJECTOR } from '../../app.config';
 import { UpperfirstPipe } from '../../pipes/upperfirst-pipe';
 import { MainHeader } from '../../components/main-header/main-header';
 import { FormGroupContact } from '../../utils/form-group-contact';
+import { LanguageManager } from '../../services/language-manager';
 
 @Component({
   selector: 'app-main',
@@ -18,7 +18,7 @@ import { FormGroupContact } from '../../utils/form-group-contact';
 })
 export class Main {
   protected readonly form = new FormGroupContact();
-  protected readonly strings = inject(STRINGS_INJECTOR);
+  protected readonly languageManager = inject(LanguageManager);
   private readonly contactService = inject(ContactService);
 
   save(contactDTO: ContactDTO) {