如何在hello world前5秒显示活动指示器

<div class="container">
  <p>Hello World</p>
  <div class="activity-indicator"></div>
</div>

.container {
  position: relative;
  text-align: center;
}

.activity-indicator {
  width: 40px;
  height: 40px;
  border: 4px solid #f3f3f3;
  border-top: 4px solid #3498db;
  border-radius: 50%;
  animation: spin 2s linear infinite;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

@keyframes spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}

window.addEventListener('DOMContentLoaded', function() {
  var activityIndicator = document.querySelector('.activity-indicator');
  setTimeout(function() {
    activityIndicator.style.display = 'none';
  }, 5000);
});