BC Break: Add method to convert patched document to array

[Konafets]

I think it is very common to convert the patched document to an array afterwards. This given, it would be nice to add a method which handles this within the lib.

I imagine an API like

$patchedArray = (new Patch($targetDocument, $patchDocument))->apply()->toArray();
$patchedDocument = (new Patch($targetDocument, $patchDocument))->apply()->toJson();

This implies that apply() does just return $this.

If this is a valuable feature I will add a PR.

[lifewcody]

I +1 this feature because I currently use: json_decode($patch->apply()); So a toArray() and toJson() via returning $this; would be very helpful

[raphaelstolt]

As this got a +1 I would accept a PR implementing this.