Vue HTML Binding - Two Way?

How do I create a two way HTML binding.

by skirtle

HTML

<div id="app">
Typing into one div should update other div!

  <div contenteditable=true v-html="message"></div>

  <div contenteditable=true v-html="message"></div>

</div>

CSS

div > div {
  margin: 40px;
  background-color: lightgray;
  padding: 5px;
}

JavaScript

new Vue({
	el: "#app",
  data: {
  	message: "Hello <b>My</b> World"
  }
});