CodePen for live site 1-4 demo does not render JSX

Running 

https://microsoft.github.io/frontend-bootcamp/step1-04/demo/

in Edge, Chrome and Firefox shows that the JSX is not rendered. Consider

```
<pre data-lang="babel">
```
or
```
<pre data-lang="typescript">
```

to load the appropriate pre-processor in codepen, or replace the JSX with `React.createElement("div", null, "Hello World")` to work with JS directly