JSON renderers

`ApplicationJSON` and `FileJSON` renderers.

`FileJSON` should provide a simple Monaco editor with some provisions for JSON editing like auto-closing curly braces and quotes.

`ApplicationJSON` should render arbitrary JSON K-V pairs as a list of heading and body text, where...

```json
{ "foo": "bar" }
```

Might be rendered as...

```
<h2>foo</h2>
<p>bar</p>
```