message: style: add background to iframes before load
diff: @@ -214,7 +214,8 @@ tbody tr:nth-child(odd) {
  background-color: var(--offset-background-color);
  }
  -.markdown-content iframe {
  +iframe {
  + background-color: rgba(0, 0, 0, 0.02);
  box-shadow: 10px 10px 20px rgba(0,0,0,0.1);
  margin: 2rem 0;
  }
  