beginning of dust integration page

This is just a start, but I think it might be good to get in to start review/discussion.

Still notably TODO is the docs for `{@formatMessage}`.
Instead of needing to style these explicitly, we can reuse the `<code>` styles but wrapping the link with `<code>...</code>`. And using the helpers it could look like this:

```handlebars
{{code (npmLink "intl-messageformat")}}
```