provide access to setCallbacks method

[ta-tikoma]

Just open access to setCallbacks method. Use case:

        $pdf = Pdf::loadView(...)->setCallbacks([
            [
                'event' => 'end_frame',
                'f' => function ($info) {
                    $frame = $info['frame'];
                    /** @var CPDF $canvas */
                    $canvas = $info['canvas'];
                    /** @var DOMElement $node */
                    $node = $frame->get_node();
                    if ($node->nodeName === 'a') {
                        $href = $node->getAttribute('href');
                        if (strpos($href, 'file://') === 0) {
                            $url = substr($href, 7);
                            foreach ($canvas->get_cpdf()->objects as $key => $object) {
                                if ($object['type'] ?? '' === 'URI') {
                                    if (strpos($object['info'] ?? '', $url) !== false) {
                                        $canvas->get_cpdf()->objects[$key]['info'] = $url;
                                        break;
                                    }
                                }
                            }
                        }
                    }
                }
            ]
        ]);

[barryvdh]

Fixed with #892