Feature/38 css general

refactor general css for the web app

src/app/modules/home/form-play-quiz/form-play-quiz.component.html

-<main class="container">
+<div class="container">
     <div class="button-header">
         <button (click)="createQuiz()">Play a quiz</button>
         <button (click)="startQuiz()">Join a quiz</button>
@@ -7,4 +7,4 @@
         <app-form-start-quiz *ngIf="showStartQuiz"></app-form-start-quiz>
         <app-form-create-quiz *ngIf="showCreateQuiz"></app-form-create-quiz>
     </div>
-</main>
+</div>
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