Improved iframe & summary handling in HTML to MD conversion

app/Entities/Tools/Markdown/HtmlToMarkdown.php

@@ -88,6 +88,7 @@ class HtmlToMarkdown
         $environment->addConverter(new PreformattedConverter());
         $environment->addConverter(new TextConverter());
         $environment->addConverter(new CheckboxConverter());
+        $environment->addConverter(new SpacedTagFallbackConverter());
 
         return $environment;
     }

app/Entities/Tools/Markdown/SpacedTagFallbackConverter.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace BookStack\Entities\Tools\Markdown;
+
+use League\HTMLToMarkdown\Converter\ConverterInterface;
+use League\HTMLToMarkdown\ElementInterface;
+
+/**
+ * For certain defined tags, add additional spacing upon the retained HTML content
+ * to separate it out from anything that may be markdown soon afterwards or within.
+ */
+class SpacedTagFallbackConverter implements ConverterInterface
+{
+    public function convert(ElementInterface $element): string
+    {
+        return \html_entity_decode($element->getChildrenAsString()) . "\n\n";
+    }
+
+    public function getSupportedTags(): array
+    {
+        return ['summary', 'iframe'];
+    }
+}