For old browser, such as IE 11. We will need to use
<script src="https://cdn.botframework.com/botframework-webchat/latest/botchat-es5.js"></script>
Instead of
<script src="https://cdn.botframework.com/botframework-webchat/latest/botchat.js"></script>
in the web page that hosts the WebChat.
And we must also include
<head>
<link href="https://cdn.botframework.com/botframework-webchat/latest/botchat.css" rel="stylesheet" />
</head>
in the same web page that hosts the WebChat.
The issue was documented at this GitHub issue.
