Comments: Switched to lexical editor

Required a lot of changes to provide at least a decent attempt at proper
editor teardown control.
Also updates HtmlDescriptionFilter and testing to address issue with bad
child iteration which could lead to missed items.
Renamed editor version from comments to basic as it'll also be used for
item descriptions.

app/Util/HtmlDescriptionFilter.php

@@ -4,7 +4,6 @@ namespace BookStack\Util;
 
 use DOMAttr;
 use DOMElement;
-use DOMNamedNodeMap;
 use DOMNode;
 
 /**
@@ -25,6 +24,7 @@ class HtmlDescriptionFilter
         'ul' => [],
         'li' => [],
         'strong' => [],
+        'span' => [],
         'em' => [],
         'br' => [],
     ];
@@ -59,7 +59,6 @@ class HtmlDescriptionFilter
             return;
         }
 
-        /** @var DOMNamedNodeMap $attrs */
         $attrs = $element->attributes;
         for ($i = $attrs->length - 1; $i >= 0; $i--) {
             /** @var DOMAttr $attr */
@@ -70,7 +69,8 @@ class HtmlDescriptionFilter
             }
         }
 
-        foreach ($element->childNodes as $child) {
+        $childNodes = [...$element->childNodes];
+        foreach ($childNodes as $child) {
             if ($child instanceof DOMElement) {
                 static::filterElement($child);
             }