将演讲气泡样式箭头添加到消息气泡上，指向消息的发件人

<div class="message-bubble">
  <div class="message-content">
    消息内容
  </div>
  <div class="speech-arrow"></div>
</div>

.message-bubble {
  background-color: #f2f2f2;
  border: 1px solid #ccc;
  border-radius: 10px;
  padding: 10px;
  position: relative;
}

.message-content {
  color: #333;
}

.speech-arrow {
  width: 0;
  height: 0;
  border-top: 10px solid transparent;
  border-bottom: 10px solid transparent;
  border-right: 10px solid #f2f2f2;
  position: absolute;
  top: 50%;
  right: -10px;
  transform: translateY(-50%);
}