Allow recursive root-level wildcards

I have found #4, but I could not find a way to select elements at any level.

For example, here I might want to operate on all `foo` elements:
```js
{
"foo": 1,
"bar": {
"foo": 2
}
}
```

- `foo` only gives `1`
- `*.foo` only gives `2`

For my use cases, it would be great to have something like `**.foo` which would give both occurrences.