Fix replaceChild() method

[ma-si]

Issue:
replaceChild() removes old child but did not add new child

Test code:

        $html = file_get_contents($source);
        $dom = new Dom();
        $dom->load($html);
        $nodes = $dom->find($node);
        foreach ($nodes as $element) {
            $text = new Dom\TextNode($replacement);
            $element->getParent()->replaceChild($element->id(), $text);
        }
        $resultHTML = $dom;

Debug:
Original result $this->children:

  1 => PHPHtmlParser\Dom\HtmlNode {#3347}
  2 => PHPHtmlParser\Dom\TextNode {#910}
  3 => PHPHtmlParser\Dom\HtmlNode {#4375}
  4 => PHPHtmlParser\Dom\TextNode {#6482}
  5 => PHPHtmlParser\Dom\HtmlNode {#889}
  6 => PHPHtmlParser\Dom\TextNode {#846}

🪲 $element->getParent()->replaceChild($element->id(), $text);

  1 => PHPHtmlParser\Dom\HtmlNode {#3347}
  2 => PHPHtmlParser\Dom\TextNode {#910}
  3 => PHPHtmlParser\Dom\HtmlNode {#4375}
  4 => PHPHtmlParser\Dom\TextNode {#6482}

Other results are OK:
$element->getParent()->removeChild($element->id());

  1 => PHPHtmlParser\Dom\HtmlNode {#3347}
  2 => PHPHtmlParser\Dom\TextNode {#910}
  3 => PHPHtmlParser\Dom\HtmlNode {#4375}
  4 => PHPHtmlParser\Dom\TextNode {#6482}
  5 => PHPHtmlParser\Dom\TextNode {#846}

$element->getParent()->addChild($text);

  1 => PHPHtmlParser\Dom\HtmlNode {#3347}
  2 => PHPHtmlParser\Dom\TextNode {#910}
  3 => PHPHtmlParser\Dom\HtmlNode {#4375}
  4 => PHPHtmlParser\Dom\TextNode {#6482}
  5 => PHPHtmlParser\Dom\HtmlNode {#889}
  6 => PHPHtmlParser\Dom\TextNode {#846}
  7 => PHPHtmlParser\Dom\TextNode {#2288}

[coveralls]

Coverage decreased (-0.5%) to 94.104% when pulling bec9ec9 on ma-si:master into 9663472 on paquettg:master.

[coveralls]

Coverage decreased (-0.5%) to 94.104% when pulling bec9ec9 on ma-si:master into 9663472 on paquettg:master.