For a recent demonstration of WVA I had to include images as part of the message response.
I ended up creating a custom layout called show-html and moved the contents of the output.text into layout.data with the html tags. By doing so the output.text was blank and hence other interfaces other than the widget did not show the content.
The feedback was good however they were puzzled why there was no out of the box support.
I note that you parse for new lines, html and email in
https://github.com/watson-virtual-agents/chat-widget/blob/master/src/utils/writeMessage.js