Document the new export(s)

### Module version

4.0.1

### What documentation problem did you notice?

When upgrading to `hapi/bourne` >= 4, the code breaks because you no longer have to do this:

```js
import Bourne from 'hapi/bourne'

// ...

parseJson: text => Bourne.safeParse(text)
```

Instead, you have to do this:

```js
import { safeParse } from '@hapi/bourne'

// ...
parseJson: text => safeParse(text)
```

The thing is, while it's really minor and I solved the problem in seconds, this change isn't documented anywhere.

Start by locating the package's usage documentation and any v4 migration notes, then compare them with the old and new examples in the issue. Document the v4 package name and named safeParse import, and verify that the current guidance no longer shows the obsolete import pattern.

Written by the indexing model from the issue text.