message: Set mat-app-background on surrounding body
diff: <meta name="description" content="An intentionally insecure JavaScript Web Application">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link id="favicon" rel="icon" type="image/x-icon" href="favicon.ico">
  - <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
  </head>
  -<body>
  +<body class="mat-app-background">
  <app-root></app-root>
  </body>
  </html>
  